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Chapter 10 Electricity
Current Dead or AliveDEATH bull NEUROLOGIC CRITERIA An individual with
irreversible cessation of all brain function including the brain stem is dead
bull CARDIOPULMONARY CRITERIA An individual with irreversible cessation of circulatory and respiratory function is dead
ElectricityElectricity
CHARGE
q = 16 x10-19 C
How many protons in a Coulomb
-19
18
100 x (1 proton) (160 x 10 ) 625 10 protons
C Cx=
Opposites Attract
Most materials are Electrically NEUTRAL(lowest potential energy)
TOTAL charge is conserved for any process
Net Zero Charge
Net Zero Charge
TOTAL charge is conserved for any processNet Charge is still zero after rubbing
Electric forces for charges that are not movingThough static charge DO move But not continuously as with current
Static Cling Adhesion
Coulombrsquos Law1 2
1 21 2 2Force between q and q q q
kq qFr
=
Likes Repel
Opposites Attract
k = 9 x 109 N m2C2
What is the Electric Force between two electrons separated by 1 mμ
1 22
9 2 2 19 2
6 2
16
(900 10 ) (160 10 ) (10 )
230 10
kq qFr
x Nm C x x Cm
x N
minus
minus
minus
=
=
=
k = 9 x 109 N m2C2
qe = -16 x10-19 (C)
16 31
14 2
230 10 9019 10 255 10
a F mx N x kgx m s
minus minus
=
=
=
k = 9 x 109 N m2C2
qe = -16 x10-19 C
What is the acceleration of one of the electrons
319019 10em x kgminus=
1 22
Ckq qF
r=
How strong is the Coulomb Force relative to Gravity
k = 9 x 109 N m2C2
G = 667 x10-11 N m2kg2
qe = 16 x10-19 C
mp = 167 x10-27 kg me = 911 x10-31 kg
r = 530 x10-11 m
1 22
GGm mF
r=
proton electron
1 22
Ckq qF
r=
How strong is the Coulomb Force relative to Gravity
1 22
GGm mF
r=
8
47
820 10
361 10C
G
F x N
F x N
minus
minus
= minus
=
proton electron
39 227 10C GF F x=
Electric FieldShows how the field acts on a POSTIVE charge
E = Forceunit Charge
What Direction are the Electric Field Lines
The Electric Field does work on the charge to move it from A to B convertingPotential Energy into Kinetic Energy same as with the gravitational field The Electric Potential Energy per unit charge between A and B is called the Electric Potential Difference between A and B -
-
HIGH V LOW V
B AV V VΔ = minus
Electric Potential
bullUnit for Electric Potential is the VOLTbull1 V = JC = N m C
bull Electric Potential is a SCALARbull Only DIFFERENCES in potential between two points can be measured There is no potential for a single pointbull Electric Potential is NOT Potential Energybull + charges move from hi to low potential
(think gravity ndash water fall)bull - charges move from low to hi potential
(think antigravity ndash water pump)
B AV V VΔ = minus
Equal Distance ndash Equal Force
A
BC
A
BC
Equal Potential
Equipotential Lines
A
BC
Where is the Potential HighestA B C
A
BC
The Electric Field is the Slope of the Electric Potential
httpwwwfalstadcomvector3de
Ohms Law V = IR
Sources of Electric Potential Batteries
15 Volt Battery is the Voltage across the terminals
ExampleA 12V motorcycle battery moves 5000C of charge How much energy does it deliver to that charge
12V V=
0PE VqΔ = Δ
12 (5000 )V C=
12 (5000 )J C C=
4600 10x J=
Potential (Voltage) is NOT Energy
Positive Charges move from HI to LOW potential
HI V LOW V
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Current Dead or AliveDEATH bull NEUROLOGIC CRITERIA An individual with
irreversible cessation of all brain function including the brain stem is dead
bull CARDIOPULMONARY CRITERIA An individual with irreversible cessation of circulatory and respiratory function is dead
ElectricityElectricity
CHARGE
q = 16 x10-19 C
How many protons in a Coulomb
-19
18
100 x (1 proton) (160 x 10 ) 625 10 protons
C Cx=
Opposites Attract
Most materials are Electrically NEUTRAL(lowest potential energy)
TOTAL charge is conserved for any process
Net Zero Charge
Net Zero Charge
TOTAL charge is conserved for any processNet Charge is still zero after rubbing
Electric forces for charges that are not movingThough static charge DO move But not continuously as with current
Static Cling Adhesion
Coulombrsquos Law1 2
1 21 2 2Force between q and q q q
kq qFr
=
Likes Repel
Opposites Attract
k = 9 x 109 N m2C2
What is the Electric Force between two electrons separated by 1 mμ
1 22
9 2 2 19 2
6 2
16
(900 10 ) (160 10 ) (10 )
230 10
kq qFr
x Nm C x x Cm
x N
minus
minus
minus
=
=
=
k = 9 x 109 N m2C2
qe = -16 x10-19 (C)
16 31
14 2
230 10 9019 10 255 10
a F mx N x kgx m s
minus minus
=
=
=
k = 9 x 109 N m2C2
qe = -16 x10-19 C
What is the acceleration of one of the electrons
319019 10em x kgminus=
1 22
Ckq qF
r=
How strong is the Coulomb Force relative to Gravity
k = 9 x 109 N m2C2
G = 667 x10-11 N m2kg2
qe = 16 x10-19 C
mp = 167 x10-27 kg me = 911 x10-31 kg
r = 530 x10-11 m
1 22
GGm mF
r=
proton electron
1 22
Ckq qF
r=
How strong is the Coulomb Force relative to Gravity
1 22
GGm mF
r=
8
47
820 10
361 10C
G
F x N
F x N
minus
minus
= minus
=
proton electron
39 227 10C GF F x=
Electric FieldShows how the field acts on a POSTIVE charge
E = Forceunit Charge
What Direction are the Electric Field Lines
The Electric Field does work on the charge to move it from A to B convertingPotential Energy into Kinetic Energy same as with the gravitational field The Electric Potential Energy per unit charge between A and B is called the Electric Potential Difference between A and B -
-
HIGH V LOW V
B AV V VΔ = minus
Electric Potential
bullUnit for Electric Potential is the VOLTbull1 V = JC = N m C
bull Electric Potential is a SCALARbull Only DIFFERENCES in potential between two points can be measured There is no potential for a single pointbull Electric Potential is NOT Potential Energybull + charges move from hi to low potential
(think gravity ndash water fall)bull - charges move from low to hi potential
(think antigravity ndash water pump)
B AV V VΔ = minus
Equal Distance ndash Equal Force
A
BC
A
BC
Equal Potential
Equipotential Lines
A
BC
Where is the Potential HighestA B C
A
BC
The Electric Field is the Slope of the Electric Potential
httpwwwfalstadcomvector3de
Ohms Law V = IR
Sources of Electric Potential Batteries
15 Volt Battery is the Voltage across the terminals
ExampleA 12V motorcycle battery moves 5000C of charge How much energy does it deliver to that charge
12V V=
0PE VqΔ = Δ
12 (5000 )V C=
12 (5000 )J C C=
4600 10x J=
Potential (Voltage) is NOT Energy
Positive Charges move from HI to LOW potential
HI V LOW V
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
ElectricityElectricity
CHARGE
q = 16 x10-19 C
How many protons in a Coulomb
-19
18
100 x (1 proton) (160 x 10 ) 625 10 protons
C Cx=
Opposites Attract
Most materials are Electrically NEUTRAL(lowest potential energy)
TOTAL charge is conserved for any process
Net Zero Charge
Net Zero Charge
TOTAL charge is conserved for any processNet Charge is still zero after rubbing
Electric forces for charges that are not movingThough static charge DO move But not continuously as with current
Static Cling Adhesion
Coulombrsquos Law1 2
1 21 2 2Force between q and q q q
kq qFr
=
Likes Repel
Opposites Attract
k = 9 x 109 N m2C2
What is the Electric Force between two electrons separated by 1 mμ
1 22
9 2 2 19 2
6 2
16
(900 10 ) (160 10 ) (10 )
230 10
kq qFr
x Nm C x x Cm
x N
minus
minus
minus
=
=
=
k = 9 x 109 N m2C2
qe = -16 x10-19 (C)
16 31
14 2
230 10 9019 10 255 10
a F mx N x kgx m s
minus minus
=
=
=
k = 9 x 109 N m2C2
qe = -16 x10-19 C
What is the acceleration of one of the electrons
319019 10em x kgminus=
1 22
Ckq qF
r=
How strong is the Coulomb Force relative to Gravity
k = 9 x 109 N m2C2
G = 667 x10-11 N m2kg2
qe = 16 x10-19 C
mp = 167 x10-27 kg me = 911 x10-31 kg
r = 530 x10-11 m
1 22
GGm mF
r=
proton electron
1 22
Ckq qF
r=
How strong is the Coulomb Force relative to Gravity
1 22
GGm mF
r=
8
47
820 10
361 10C
G
F x N
F x N
minus
minus
= minus
=
proton electron
39 227 10C GF F x=
Electric FieldShows how the field acts on a POSTIVE charge
E = Forceunit Charge
What Direction are the Electric Field Lines
The Electric Field does work on the charge to move it from A to B convertingPotential Energy into Kinetic Energy same as with the gravitational field The Electric Potential Energy per unit charge between A and B is called the Electric Potential Difference between A and B -
-
HIGH V LOW V
B AV V VΔ = minus
Electric Potential
bullUnit for Electric Potential is the VOLTbull1 V = JC = N m C
bull Electric Potential is a SCALARbull Only DIFFERENCES in potential between two points can be measured There is no potential for a single pointbull Electric Potential is NOT Potential Energybull + charges move from hi to low potential
(think gravity ndash water fall)bull - charges move from low to hi potential
(think antigravity ndash water pump)
B AV V VΔ = minus
Equal Distance ndash Equal Force
A
BC
A
BC
Equal Potential
Equipotential Lines
A
BC
Where is the Potential HighestA B C
A
BC
The Electric Field is the Slope of the Electric Potential
httpwwwfalstadcomvector3de
Ohms Law V = IR
Sources of Electric Potential Batteries
15 Volt Battery is the Voltage across the terminals
ExampleA 12V motorcycle battery moves 5000C of charge How much energy does it deliver to that charge
12V V=
0PE VqΔ = Δ
12 (5000 )V C=
12 (5000 )J C C=
4600 10x J=
Potential (Voltage) is NOT Energy
Positive Charges move from HI to LOW potential
HI V LOW V
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
How many protons in a Coulomb
-19
18
100 x (1 proton) (160 x 10 ) 625 10 protons
C Cx=
Opposites Attract
Most materials are Electrically NEUTRAL(lowest potential energy)
TOTAL charge is conserved for any process
Net Zero Charge
Net Zero Charge
TOTAL charge is conserved for any processNet Charge is still zero after rubbing
Electric forces for charges that are not movingThough static charge DO move But not continuously as with current
Static Cling Adhesion
Coulombrsquos Law1 2
1 21 2 2Force between q and q q q
kq qFr
=
Likes Repel
Opposites Attract
k = 9 x 109 N m2C2
What is the Electric Force between two electrons separated by 1 mμ
1 22
9 2 2 19 2
6 2
16
(900 10 ) (160 10 ) (10 )
230 10
kq qFr
x Nm C x x Cm
x N
minus
minus
minus
=
=
=
k = 9 x 109 N m2C2
qe = -16 x10-19 (C)
16 31
14 2
230 10 9019 10 255 10
a F mx N x kgx m s
minus minus
=
=
=
k = 9 x 109 N m2C2
qe = -16 x10-19 C
What is the acceleration of one of the electrons
319019 10em x kgminus=
1 22
Ckq qF
r=
How strong is the Coulomb Force relative to Gravity
k = 9 x 109 N m2C2
G = 667 x10-11 N m2kg2
qe = 16 x10-19 C
mp = 167 x10-27 kg me = 911 x10-31 kg
r = 530 x10-11 m
1 22
GGm mF
r=
proton electron
1 22
Ckq qF
r=
How strong is the Coulomb Force relative to Gravity
1 22
GGm mF
r=
8
47
820 10
361 10C
G
F x N
F x N
minus
minus
= minus
=
proton electron
39 227 10C GF F x=
Electric FieldShows how the field acts on a POSTIVE charge
E = Forceunit Charge
What Direction are the Electric Field Lines
The Electric Field does work on the charge to move it from A to B convertingPotential Energy into Kinetic Energy same as with the gravitational field The Electric Potential Energy per unit charge between A and B is called the Electric Potential Difference between A and B -
-
HIGH V LOW V
B AV V VΔ = minus
Electric Potential
bullUnit for Electric Potential is the VOLTbull1 V = JC = N m C
bull Electric Potential is a SCALARbull Only DIFFERENCES in potential between two points can be measured There is no potential for a single pointbull Electric Potential is NOT Potential Energybull + charges move from hi to low potential
(think gravity ndash water fall)bull - charges move from low to hi potential
(think antigravity ndash water pump)
B AV V VΔ = minus
Equal Distance ndash Equal Force
A
BC
A
BC
Equal Potential
Equipotential Lines
A
BC
Where is the Potential HighestA B C
A
BC
The Electric Field is the Slope of the Electric Potential
httpwwwfalstadcomvector3de
Ohms Law V = IR
Sources of Electric Potential Batteries
15 Volt Battery is the Voltage across the terminals
ExampleA 12V motorcycle battery moves 5000C of charge How much energy does it deliver to that charge
12V V=
0PE VqΔ = Δ
12 (5000 )V C=
12 (5000 )J C C=
4600 10x J=
Potential (Voltage) is NOT Energy
Positive Charges move from HI to LOW potential
HI V LOW V
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Opposites Attract
Most materials are Electrically NEUTRAL(lowest potential energy)
TOTAL charge is conserved for any process
Net Zero Charge
Net Zero Charge
TOTAL charge is conserved for any processNet Charge is still zero after rubbing
Electric forces for charges that are not movingThough static charge DO move But not continuously as with current
Static Cling Adhesion
Coulombrsquos Law1 2
1 21 2 2Force between q and q q q
kq qFr
=
Likes Repel
Opposites Attract
k = 9 x 109 N m2C2
What is the Electric Force between two electrons separated by 1 mμ
1 22
9 2 2 19 2
6 2
16
(900 10 ) (160 10 ) (10 )
230 10
kq qFr
x Nm C x x Cm
x N
minus
minus
minus
=
=
=
k = 9 x 109 N m2C2
qe = -16 x10-19 (C)
16 31
14 2
230 10 9019 10 255 10
a F mx N x kgx m s
minus minus
=
=
=
k = 9 x 109 N m2C2
qe = -16 x10-19 C
What is the acceleration of one of the electrons
319019 10em x kgminus=
1 22
Ckq qF
r=
How strong is the Coulomb Force relative to Gravity
k = 9 x 109 N m2C2
G = 667 x10-11 N m2kg2
qe = 16 x10-19 C
mp = 167 x10-27 kg me = 911 x10-31 kg
r = 530 x10-11 m
1 22
GGm mF
r=
proton electron
1 22
Ckq qF
r=
How strong is the Coulomb Force relative to Gravity
1 22
GGm mF
r=
8
47
820 10
361 10C
G
F x N
F x N
minus
minus
= minus
=
proton electron
39 227 10C GF F x=
Electric FieldShows how the field acts on a POSTIVE charge
E = Forceunit Charge
What Direction are the Electric Field Lines
The Electric Field does work on the charge to move it from A to B convertingPotential Energy into Kinetic Energy same as with the gravitational field The Electric Potential Energy per unit charge between A and B is called the Electric Potential Difference between A and B -
-
HIGH V LOW V
B AV V VΔ = minus
Electric Potential
bullUnit for Electric Potential is the VOLTbull1 V = JC = N m C
bull Electric Potential is a SCALARbull Only DIFFERENCES in potential between two points can be measured There is no potential for a single pointbull Electric Potential is NOT Potential Energybull + charges move from hi to low potential
(think gravity ndash water fall)bull - charges move from low to hi potential
(think antigravity ndash water pump)
B AV V VΔ = minus
Equal Distance ndash Equal Force
A
BC
A
BC
Equal Potential
Equipotential Lines
A
BC
Where is the Potential HighestA B C
A
BC
The Electric Field is the Slope of the Electric Potential
httpwwwfalstadcomvector3de
Ohms Law V = IR
Sources of Electric Potential Batteries
15 Volt Battery is the Voltage across the terminals
ExampleA 12V motorcycle battery moves 5000C of charge How much energy does it deliver to that charge
12V V=
0PE VqΔ = Δ
12 (5000 )V C=
12 (5000 )J C C=
4600 10x J=
Potential (Voltage) is NOT Energy
Positive Charges move from HI to LOW potential
HI V LOW V
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Most materials are Electrically NEUTRAL(lowest potential energy)
TOTAL charge is conserved for any process
Net Zero Charge
Net Zero Charge
TOTAL charge is conserved for any processNet Charge is still zero after rubbing
Electric forces for charges that are not movingThough static charge DO move But not continuously as with current
Static Cling Adhesion
Coulombrsquos Law1 2
1 21 2 2Force between q and q q q
kq qFr
=
Likes Repel
Opposites Attract
k = 9 x 109 N m2C2
What is the Electric Force between two electrons separated by 1 mμ
1 22
9 2 2 19 2
6 2
16
(900 10 ) (160 10 ) (10 )
230 10
kq qFr
x Nm C x x Cm
x N
minus
minus
minus
=
=
=
k = 9 x 109 N m2C2
qe = -16 x10-19 (C)
16 31
14 2
230 10 9019 10 255 10
a F mx N x kgx m s
minus minus
=
=
=
k = 9 x 109 N m2C2
qe = -16 x10-19 C
What is the acceleration of one of the electrons
319019 10em x kgminus=
1 22
Ckq qF
r=
How strong is the Coulomb Force relative to Gravity
k = 9 x 109 N m2C2
G = 667 x10-11 N m2kg2
qe = 16 x10-19 C
mp = 167 x10-27 kg me = 911 x10-31 kg
r = 530 x10-11 m
1 22
GGm mF
r=
proton electron
1 22
Ckq qF
r=
How strong is the Coulomb Force relative to Gravity
1 22
GGm mF
r=
8
47
820 10
361 10C
G
F x N
F x N
minus
minus
= minus
=
proton electron
39 227 10C GF F x=
Electric FieldShows how the field acts on a POSTIVE charge
E = Forceunit Charge
What Direction are the Electric Field Lines
The Electric Field does work on the charge to move it from A to B convertingPotential Energy into Kinetic Energy same as with the gravitational field The Electric Potential Energy per unit charge between A and B is called the Electric Potential Difference between A and B -
-
HIGH V LOW V
B AV V VΔ = minus
Electric Potential
bullUnit for Electric Potential is the VOLTbull1 V = JC = N m C
bull Electric Potential is a SCALARbull Only DIFFERENCES in potential between two points can be measured There is no potential for a single pointbull Electric Potential is NOT Potential Energybull + charges move from hi to low potential
(think gravity ndash water fall)bull - charges move from low to hi potential
(think antigravity ndash water pump)
B AV V VΔ = minus
Equal Distance ndash Equal Force
A
BC
A
BC
Equal Potential
Equipotential Lines
A
BC
Where is the Potential HighestA B C
A
BC
The Electric Field is the Slope of the Electric Potential
httpwwwfalstadcomvector3de
Ohms Law V = IR
Sources of Electric Potential Batteries
15 Volt Battery is the Voltage across the terminals
ExampleA 12V motorcycle battery moves 5000C of charge How much energy does it deliver to that charge
12V V=
0PE VqΔ = Δ
12 (5000 )V C=
12 (5000 )J C C=
4600 10x J=
Potential (Voltage) is NOT Energy
Positive Charges move from HI to LOW potential
HI V LOW V
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
TOTAL charge is conserved for any process
Net Zero Charge
Net Zero Charge
TOTAL charge is conserved for any processNet Charge is still zero after rubbing
Electric forces for charges that are not movingThough static charge DO move But not continuously as with current
Static Cling Adhesion
Coulombrsquos Law1 2
1 21 2 2Force between q and q q q
kq qFr
=
Likes Repel
Opposites Attract
k = 9 x 109 N m2C2
What is the Electric Force between two electrons separated by 1 mμ
1 22
9 2 2 19 2
6 2
16
(900 10 ) (160 10 ) (10 )
230 10
kq qFr
x Nm C x x Cm
x N
minus
minus
minus
=
=
=
k = 9 x 109 N m2C2
qe = -16 x10-19 (C)
16 31
14 2
230 10 9019 10 255 10
a F mx N x kgx m s
minus minus
=
=
=
k = 9 x 109 N m2C2
qe = -16 x10-19 C
What is the acceleration of one of the electrons
319019 10em x kgminus=
1 22
Ckq qF
r=
How strong is the Coulomb Force relative to Gravity
k = 9 x 109 N m2C2
G = 667 x10-11 N m2kg2
qe = 16 x10-19 C
mp = 167 x10-27 kg me = 911 x10-31 kg
r = 530 x10-11 m
1 22
GGm mF
r=
proton electron
1 22
Ckq qF
r=
How strong is the Coulomb Force relative to Gravity
1 22
GGm mF
r=
8
47
820 10
361 10C
G
F x N
F x N
minus
minus
= minus
=
proton electron
39 227 10C GF F x=
Electric FieldShows how the field acts on a POSTIVE charge
E = Forceunit Charge
What Direction are the Electric Field Lines
The Electric Field does work on the charge to move it from A to B convertingPotential Energy into Kinetic Energy same as with the gravitational field The Electric Potential Energy per unit charge between A and B is called the Electric Potential Difference between A and B -
-
HIGH V LOW V
B AV V VΔ = minus
Electric Potential
bullUnit for Electric Potential is the VOLTbull1 V = JC = N m C
bull Electric Potential is a SCALARbull Only DIFFERENCES in potential between two points can be measured There is no potential for a single pointbull Electric Potential is NOT Potential Energybull + charges move from hi to low potential
(think gravity ndash water fall)bull - charges move from low to hi potential
(think antigravity ndash water pump)
B AV V VΔ = minus
Equal Distance ndash Equal Force
A
BC
A
BC
Equal Potential
Equipotential Lines
A
BC
Where is the Potential HighestA B C
A
BC
The Electric Field is the Slope of the Electric Potential
httpwwwfalstadcomvector3de
Ohms Law V = IR
Sources of Electric Potential Batteries
15 Volt Battery is the Voltage across the terminals
ExampleA 12V motorcycle battery moves 5000C of charge How much energy does it deliver to that charge
12V V=
0PE VqΔ = Δ
12 (5000 )V C=
12 (5000 )J C C=
4600 10x J=
Potential (Voltage) is NOT Energy
Positive Charges move from HI to LOW potential
HI V LOW V
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
TOTAL charge is conserved for any processNet Charge is still zero after rubbing
Electric forces for charges that are not movingThough static charge DO move But not continuously as with current
Static Cling Adhesion
Coulombrsquos Law1 2
1 21 2 2Force between q and q q q
kq qFr
=
Likes Repel
Opposites Attract
k = 9 x 109 N m2C2
What is the Electric Force between two electrons separated by 1 mμ
1 22
9 2 2 19 2
6 2
16
(900 10 ) (160 10 ) (10 )
230 10
kq qFr
x Nm C x x Cm
x N
minus
minus
minus
=
=
=
k = 9 x 109 N m2C2
qe = -16 x10-19 (C)
16 31
14 2
230 10 9019 10 255 10
a F mx N x kgx m s
minus minus
=
=
=
k = 9 x 109 N m2C2
qe = -16 x10-19 C
What is the acceleration of one of the electrons
319019 10em x kgminus=
1 22
Ckq qF
r=
How strong is the Coulomb Force relative to Gravity
k = 9 x 109 N m2C2
G = 667 x10-11 N m2kg2
qe = 16 x10-19 C
mp = 167 x10-27 kg me = 911 x10-31 kg
r = 530 x10-11 m
1 22
GGm mF
r=
proton electron
1 22
Ckq qF
r=
How strong is the Coulomb Force relative to Gravity
1 22
GGm mF
r=
8
47
820 10
361 10C
G
F x N
F x N
minus
minus
= minus
=
proton electron
39 227 10C GF F x=
Electric FieldShows how the field acts on a POSTIVE charge
E = Forceunit Charge
What Direction are the Electric Field Lines
The Electric Field does work on the charge to move it from A to B convertingPotential Energy into Kinetic Energy same as with the gravitational field The Electric Potential Energy per unit charge between A and B is called the Electric Potential Difference between A and B -
-
HIGH V LOW V
B AV V VΔ = minus
Electric Potential
bullUnit for Electric Potential is the VOLTbull1 V = JC = N m C
bull Electric Potential is a SCALARbull Only DIFFERENCES in potential between two points can be measured There is no potential for a single pointbull Electric Potential is NOT Potential Energybull + charges move from hi to low potential
(think gravity ndash water fall)bull - charges move from low to hi potential
(think antigravity ndash water pump)
B AV V VΔ = minus
Equal Distance ndash Equal Force
A
BC
A
BC
Equal Potential
Equipotential Lines
A
BC
Where is the Potential HighestA B C
A
BC
The Electric Field is the Slope of the Electric Potential
httpwwwfalstadcomvector3de
Ohms Law V = IR
Sources of Electric Potential Batteries
15 Volt Battery is the Voltage across the terminals
ExampleA 12V motorcycle battery moves 5000C of charge How much energy does it deliver to that charge
12V V=
0PE VqΔ = Δ
12 (5000 )V C=
12 (5000 )J C C=
4600 10x J=
Potential (Voltage) is NOT Energy
Positive Charges move from HI to LOW potential
HI V LOW V
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Electric forces for charges that are not movingThough static charge DO move But not continuously as with current
Static Cling Adhesion
Coulombrsquos Law1 2
1 21 2 2Force between q and q q q
kq qFr
=
Likes Repel
Opposites Attract
k = 9 x 109 N m2C2
What is the Electric Force between two electrons separated by 1 mμ
1 22
9 2 2 19 2
6 2
16
(900 10 ) (160 10 ) (10 )
230 10
kq qFr
x Nm C x x Cm
x N
minus
minus
minus
=
=
=
k = 9 x 109 N m2C2
qe = -16 x10-19 (C)
16 31
14 2
230 10 9019 10 255 10
a F mx N x kgx m s
minus minus
=
=
=
k = 9 x 109 N m2C2
qe = -16 x10-19 C
What is the acceleration of one of the electrons
319019 10em x kgminus=
1 22
Ckq qF
r=
How strong is the Coulomb Force relative to Gravity
k = 9 x 109 N m2C2
G = 667 x10-11 N m2kg2
qe = 16 x10-19 C
mp = 167 x10-27 kg me = 911 x10-31 kg
r = 530 x10-11 m
1 22
GGm mF
r=
proton electron
1 22
Ckq qF
r=
How strong is the Coulomb Force relative to Gravity
1 22
GGm mF
r=
8
47
820 10
361 10C
G
F x N
F x N
minus
minus
= minus
=
proton electron
39 227 10C GF F x=
Electric FieldShows how the field acts on a POSTIVE charge
E = Forceunit Charge
What Direction are the Electric Field Lines
The Electric Field does work on the charge to move it from A to B convertingPotential Energy into Kinetic Energy same as with the gravitational field The Electric Potential Energy per unit charge between A and B is called the Electric Potential Difference between A and B -
-
HIGH V LOW V
B AV V VΔ = minus
Electric Potential
bullUnit for Electric Potential is the VOLTbull1 V = JC = N m C
bull Electric Potential is a SCALARbull Only DIFFERENCES in potential between two points can be measured There is no potential for a single pointbull Electric Potential is NOT Potential Energybull + charges move from hi to low potential
(think gravity ndash water fall)bull - charges move from low to hi potential
(think antigravity ndash water pump)
B AV V VΔ = minus
Equal Distance ndash Equal Force
A
BC
A
BC
Equal Potential
Equipotential Lines
A
BC
Where is the Potential HighestA B C
A
BC
The Electric Field is the Slope of the Electric Potential
httpwwwfalstadcomvector3de
Ohms Law V = IR
Sources of Electric Potential Batteries
15 Volt Battery is the Voltage across the terminals
ExampleA 12V motorcycle battery moves 5000C of charge How much energy does it deliver to that charge
12V V=
0PE VqΔ = Δ
12 (5000 )V C=
12 (5000 )J C C=
4600 10x J=
Potential (Voltage) is NOT Energy
Positive Charges move from HI to LOW potential
HI V LOW V
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Coulombrsquos Law1 2
1 21 2 2Force between q and q q q
kq qFr
=
Likes Repel
Opposites Attract
k = 9 x 109 N m2C2
What is the Electric Force between two electrons separated by 1 mμ
1 22
9 2 2 19 2
6 2
16
(900 10 ) (160 10 ) (10 )
230 10
kq qFr
x Nm C x x Cm
x N
minus
minus
minus
=
=
=
k = 9 x 109 N m2C2
qe = -16 x10-19 (C)
16 31
14 2
230 10 9019 10 255 10
a F mx N x kgx m s
minus minus
=
=
=
k = 9 x 109 N m2C2
qe = -16 x10-19 C
What is the acceleration of one of the electrons
319019 10em x kgminus=
1 22
Ckq qF
r=
How strong is the Coulomb Force relative to Gravity
k = 9 x 109 N m2C2
G = 667 x10-11 N m2kg2
qe = 16 x10-19 C
mp = 167 x10-27 kg me = 911 x10-31 kg
r = 530 x10-11 m
1 22
GGm mF
r=
proton electron
1 22
Ckq qF
r=
How strong is the Coulomb Force relative to Gravity
1 22
GGm mF
r=
8
47
820 10
361 10C
G
F x N
F x N
minus
minus
= minus
=
proton electron
39 227 10C GF F x=
Electric FieldShows how the field acts on a POSTIVE charge
E = Forceunit Charge
What Direction are the Electric Field Lines
The Electric Field does work on the charge to move it from A to B convertingPotential Energy into Kinetic Energy same as with the gravitational field The Electric Potential Energy per unit charge between A and B is called the Electric Potential Difference between A and B -
-
HIGH V LOW V
B AV V VΔ = minus
Electric Potential
bullUnit for Electric Potential is the VOLTbull1 V = JC = N m C
bull Electric Potential is a SCALARbull Only DIFFERENCES in potential between two points can be measured There is no potential for a single pointbull Electric Potential is NOT Potential Energybull + charges move from hi to low potential
(think gravity ndash water fall)bull - charges move from low to hi potential
(think antigravity ndash water pump)
B AV V VΔ = minus
Equal Distance ndash Equal Force
A
BC
A
BC
Equal Potential
Equipotential Lines
A
BC
Where is the Potential HighestA B C
A
BC
The Electric Field is the Slope of the Electric Potential
httpwwwfalstadcomvector3de
Ohms Law V = IR
Sources of Electric Potential Batteries
15 Volt Battery is the Voltage across the terminals
ExampleA 12V motorcycle battery moves 5000C of charge How much energy does it deliver to that charge
12V V=
0PE VqΔ = Δ
12 (5000 )V C=
12 (5000 )J C C=
4600 10x J=
Potential (Voltage) is NOT Energy
Positive Charges move from HI to LOW potential
HI V LOW V
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
What is the Electric Force between two electrons separated by 1 mμ
1 22
9 2 2 19 2
6 2
16
(900 10 ) (160 10 ) (10 )
230 10
kq qFr
x Nm C x x Cm
x N
minus
minus
minus
=
=
=
k = 9 x 109 N m2C2
qe = -16 x10-19 (C)
16 31
14 2
230 10 9019 10 255 10
a F mx N x kgx m s
minus minus
=
=
=
k = 9 x 109 N m2C2
qe = -16 x10-19 C
What is the acceleration of one of the electrons
319019 10em x kgminus=
1 22
Ckq qF
r=
How strong is the Coulomb Force relative to Gravity
k = 9 x 109 N m2C2
G = 667 x10-11 N m2kg2
qe = 16 x10-19 C
mp = 167 x10-27 kg me = 911 x10-31 kg
r = 530 x10-11 m
1 22
GGm mF
r=
proton electron
1 22
Ckq qF
r=
How strong is the Coulomb Force relative to Gravity
1 22
GGm mF
r=
8
47
820 10
361 10C
G
F x N
F x N
minus
minus
= minus
=
proton electron
39 227 10C GF F x=
Electric FieldShows how the field acts on a POSTIVE charge
E = Forceunit Charge
What Direction are the Electric Field Lines
The Electric Field does work on the charge to move it from A to B convertingPotential Energy into Kinetic Energy same as with the gravitational field The Electric Potential Energy per unit charge between A and B is called the Electric Potential Difference between A and B -
-
HIGH V LOW V
B AV V VΔ = minus
Electric Potential
bullUnit for Electric Potential is the VOLTbull1 V = JC = N m C
bull Electric Potential is a SCALARbull Only DIFFERENCES in potential between two points can be measured There is no potential for a single pointbull Electric Potential is NOT Potential Energybull + charges move from hi to low potential
(think gravity ndash water fall)bull - charges move from low to hi potential
(think antigravity ndash water pump)
B AV V VΔ = minus
Equal Distance ndash Equal Force
A
BC
A
BC
Equal Potential
Equipotential Lines
A
BC
Where is the Potential HighestA B C
A
BC
The Electric Field is the Slope of the Electric Potential
httpwwwfalstadcomvector3de
Ohms Law V = IR
Sources of Electric Potential Batteries
15 Volt Battery is the Voltage across the terminals
ExampleA 12V motorcycle battery moves 5000C of charge How much energy does it deliver to that charge
12V V=
0PE VqΔ = Δ
12 (5000 )V C=
12 (5000 )J C C=
4600 10x J=
Potential (Voltage) is NOT Energy
Positive Charges move from HI to LOW potential
HI V LOW V
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
16 31
14 2
230 10 9019 10 255 10
a F mx N x kgx m s
minus minus
=
=
=
k = 9 x 109 N m2C2
qe = -16 x10-19 C
What is the acceleration of one of the electrons
319019 10em x kgminus=
1 22
Ckq qF
r=
How strong is the Coulomb Force relative to Gravity
k = 9 x 109 N m2C2
G = 667 x10-11 N m2kg2
qe = 16 x10-19 C
mp = 167 x10-27 kg me = 911 x10-31 kg
r = 530 x10-11 m
1 22
GGm mF
r=
proton electron
1 22
Ckq qF
r=
How strong is the Coulomb Force relative to Gravity
1 22
GGm mF
r=
8
47
820 10
361 10C
G
F x N
F x N
minus
minus
= minus
=
proton electron
39 227 10C GF F x=
Electric FieldShows how the field acts on a POSTIVE charge
E = Forceunit Charge
What Direction are the Electric Field Lines
The Electric Field does work on the charge to move it from A to B convertingPotential Energy into Kinetic Energy same as with the gravitational field The Electric Potential Energy per unit charge between A and B is called the Electric Potential Difference between A and B -
-
HIGH V LOW V
B AV V VΔ = minus
Electric Potential
bullUnit for Electric Potential is the VOLTbull1 V = JC = N m C
bull Electric Potential is a SCALARbull Only DIFFERENCES in potential between two points can be measured There is no potential for a single pointbull Electric Potential is NOT Potential Energybull + charges move from hi to low potential
(think gravity ndash water fall)bull - charges move from low to hi potential
(think antigravity ndash water pump)
B AV V VΔ = minus
Equal Distance ndash Equal Force
A
BC
A
BC
Equal Potential
Equipotential Lines
A
BC
Where is the Potential HighestA B C
A
BC
The Electric Field is the Slope of the Electric Potential
httpwwwfalstadcomvector3de
Ohms Law V = IR
Sources of Electric Potential Batteries
15 Volt Battery is the Voltage across the terminals
ExampleA 12V motorcycle battery moves 5000C of charge How much energy does it deliver to that charge
12V V=
0PE VqΔ = Δ
12 (5000 )V C=
12 (5000 )J C C=
4600 10x J=
Potential (Voltage) is NOT Energy
Positive Charges move from HI to LOW potential
HI V LOW V
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
1 22
Ckq qF
r=
How strong is the Coulomb Force relative to Gravity
k = 9 x 109 N m2C2
G = 667 x10-11 N m2kg2
qe = 16 x10-19 C
mp = 167 x10-27 kg me = 911 x10-31 kg
r = 530 x10-11 m
1 22
GGm mF
r=
proton electron
1 22
Ckq qF
r=
How strong is the Coulomb Force relative to Gravity
1 22
GGm mF
r=
8
47
820 10
361 10C
G
F x N
F x N
minus
minus
= minus
=
proton electron
39 227 10C GF F x=
Electric FieldShows how the field acts on a POSTIVE charge
E = Forceunit Charge
What Direction are the Electric Field Lines
The Electric Field does work on the charge to move it from A to B convertingPotential Energy into Kinetic Energy same as with the gravitational field The Electric Potential Energy per unit charge between A and B is called the Electric Potential Difference between A and B -
-
HIGH V LOW V
B AV V VΔ = minus
Electric Potential
bullUnit for Electric Potential is the VOLTbull1 V = JC = N m C
bull Electric Potential is a SCALARbull Only DIFFERENCES in potential between two points can be measured There is no potential for a single pointbull Electric Potential is NOT Potential Energybull + charges move from hi to low potential
(think gravity ndash water fall)bull - charges move from low to hi potential
(think antigravity ndash water pump)
B AV V VΔ = minus
Equal Distance ndash Equal Force
A
BC
A
BC
Equal Potential
Equipotential Lines
A
BC
Where is the Potential HighestA B C
A
BC
The Electric Field is the Slope of the Electric Potential
httpwwwfalstadcomvector3de
Ohms Law V = IR
Sources of Electric Potential Batteries
15 Volt Battery is the Voltage across the terminals
ExampleA 12V motorcycle battery moves 5000C of charge How much energy does it deliver to that charge
12V V=
0PE VqΔ = Δ
12 (5000 )V C=
12 (5000 )J C C=
4600 10x J=
Potential (Voltage) is NOT Energy
Positive Charges move from HI to LOW potential
HI V LOW V
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
1 22
Ckq qF
r=
How strong is the Coulomb Force relative to Gravity
1 22
GGm mF
r=
8
47
820 10
361 10C
G
F x N
F x N
minus
minus
= minus
=
proton electron
39 227 10C GF F x=
Electric FieldShows how the field acts on a POSTIVE charge
E = Forceunit Charge
What Direction are the Electric Field Lines
The Electric Field does work on the charge to move it from A to B convertingPotential Energy into Kinetic Energy same as with the gravitational field The Electric Potential Energy per unit charge between A and B is called the Electric Potential Difference between A and B -
-
HIGH V LOW V
B AV V VΔ = minus
Electric Potential
bullUnit for Electric Potential is the VOLTbull1 V = JC = N m C
bull Electric Potential is a SCALARbull Only DIFFERENCES in potential between two points can be measured There is no potential for a single pointbull Electric Potential is NOT Potential Energybull + charges move from hi to low potential
(think gravity ndash water fall)bull - charges move from low to hi potential
(think antigravity ndash water pump)
B AV V VΔ = minus
Equal Distance ndash Equal Force
A
BC
A
BC
Equal Potential
Equipotential Lines
A
BC
Where is the Potential HighestA B C
A
BC
The Electric Field is the Slope of the Electric Potential
httpwwwfalstadcomvector3de
Ohms Law V = IR
Sources of Electric Potential Batteries
15 Volt Battery is the Voltage across the terminals
ExampleA 12V motorcycle battery moves 5000C of charge How much energy does it deliver to that charge
12V V=
0PE VqΔ = Δ
12 (5000 )V C=
12 (5000 )J C C=
4600 10x J=
Potential (Voltage) is NOT Energy
Positive Charges move from HI to LOW potential
HI V LOW V
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Electric FieldShows how the field acts on a POSTIVE charge
E = Forceunit Charge
What Direction are the Electric Field Lines
The Electric Field does work on the charge to move it from A to B convertingPotential Energy into Kinetic Energy same as with the gravitational field The Electric Potential Energy per unit charge between A and B is called the Electric Potential Difference between A and B -
-
HIGH V LOW V
B AV V VΔ = minus
Electric Potential
bullUnit for Electric Potential is the VOLTbull1 V = JC = N m C
bull Electric Potential is a SCALARbull Only DIFFERENCES in potential between two points can be measured There is no potential for a single pointbull Electric Potential is NOT Potential Energybull + charges move from hi to low potential
(think gravity ndash water fall)bull - charges move from low to hi potential
(think antigravity ndash water pump)
B AV V VΔ = minus
Equal Distance ndash Equal Force
A
BC
A
BC
Equal Potential
Equipotential Lines
A
BC
Where is the Potential HighestA B C
A
BC
The Electric Field is the Slope of the Electric Potential
httpwwwfalstadcomvector3de
Ohms Law V = IR
Sources of Electric Potential Batteries
15 Volt Battery is the Voltage across the terminals
ExampleA 12V motorcycle battery moves 5000C of charge How much energy does it deliver to that charge
12V V=
0PE VqΔ = Δ
12 (5000 )V C=
12 (5000 )J C C=
4600 10x J=
Potential (Voltage) is NOT Energy
Positive Charges move from HI to LOW potential
HI V LOW V
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
What Direction are the Electric Field Lines
The Electric Field does work on the charge to move it from A to B convertingPotential Energy into Kinetic Energy same as with the gravitational field The Electric Potential Energy per unit charge between A and B is called the Electric Potential Difference between A and B -
-
HIGH V LOW V
B AV V VΔ = minus
Electric Potential
bullUnit for Electric Potential is the VOLTbull1 V = JC = N m C
bull Electric Potential is a SCALARbull Only DIFFERENCES in potential between two points can be measured There is no potential for a single pointbull Electric Potential is NOT Potential Energybull + charges move from hi to low potential
(think gravity ndash water fall)bull - charges move from low to hi potential
(think antigravity ndash water pump)
B AV V VΔ = minus
Equal Distance ndash Equal Force
A
BC
A
BC
Equal Potential
Equipotential Lines
A
BC
Where is the Potential HighestA B C
A
BC
The Electric Field is the Slope of the Electric Potential
httpwwwfalstadcomvector3de
Ohms Law V = IR
Sources of Electric Potential Batteries
15 Volt Battery is the Voltage across the terminals
ExampleA 12V motorcycle battery moves 5000C of charge How much energy does it deliver to that charge
12V V=
0PE VqΔ = Δ
12 (5000 )V C=
12 (5000 )J C C=
4600 10x J=
Potential (Voltage) is NOT Energy
Positive Charges move from HI to LOW potential
HI V LOW V
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
The Electric Field does work on the charge to move it from A to B convertingPotential Energy into Kinetic Energy same as with the gravitational field The Electric Potential Energy per unit charge between A and B is called the Electric Potential Difference between A and B -
-
HIGH V LOW V
B AV V VΔ = minus
Electric Potential
bullUnit for Electric Potential is the VOLTbull1 V = JC = N m C
bull Electric Potential is a SCALARbull Only DIFFERENCES in potential between two points can be measured There is no potential for a single pointbull Electric Potential is NOT Potential Energybull + charges move from hi to low potential
(think gravity ndash water fall)bull - charges move from low to hi potential
(think antigravity ndash water pump)
B AV V VΔ = minus
Equal Distance ndash Equal Force
A
BC
A
BC
Equal Potential
Equipotential Lines
A
BC
Where is the Potential HighestA B C
A
BC
The Electric Field is the Slope of the Electric Potential
httpwwwfalstadcomvector3de
Ohms Law V = IR
Sources of Electric Potential Batteries
15 Volt Battery is the Voltage across the terminals
ExampleA 12V motorcycle battery moves 5000C of charge How much energy does it deliver to that charge
12V V=
0PE VqΔ = Δ
12 (5000 )V C=
12 (5000 )J C C=
4600 10x J=
Potential (Voltage) is NOT Energy
Positive Charges move from HI to LOW potential
HI V LOW V
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Electric Potential
bullUnit for Electric Potential is the VOLTbull1 V = JC = N m C
bull Electric Potential is a SCALARbull Only DIFFERENCES in potential between two points can be measured There is no potential for a single pointbull Electric Potential is NOT Potential Energybull + charges move from hi to low potential
(think gravity ndash water fall)bull - charges move from low to hi potential
(think antigravity ndash water pump)
B AV V VΔ = minus
Equal Distance ndash Equal Force
A
BC
A
BC
Equal Potential
Equipotential Lines
A
BC
Where is the Potential HighestA B C
A
BC
The Electric Field is the Slope of the Electric Potential
httpwwwfalstadcomvector3de
Ohms Law V = IR
Sources of Electric Potential Batteries
15 Volt Battery is the Voltage across the terminals
ExampleA 12V motorcycle battery moves 5000C of charge How much energy does it deliver to that charge
12V V=
0PE VqΔ = Δ
12 (5000 )V C=
12 (5000 )J C C=
4600 10x J=
Potential (Voltage) is NOT Energy
Positive Charges move from HI to LOW potential
HI V LOW V
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Equal Distance ndash Equal Force
A
BC
A
BC
Equal Potential
Equipotential Lines
A
BC
Where is the Potential HighestA B C
A
BC
The Electric Field is the Slope of the Electric Potential
httpwwwfalstadcomvector3de
Ohms Law V = IR
Sources of Electric Potential Batteries
15 Volt Battery is the Voltage across the terminals
ExampleA 12V motorcycle battery moves 5000C of charge How much energy does it deliver to that charge
12V V=
0PE VqΔ = Δ
12 (5000 )V C=
12 (5000 )J C C=
4600 10x J=
Potential (Voltage) is NOT Energy
Positive Charges move from HI to LOW potential
HI V LOW V
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
A
BC
Equal Potential
Equipotential Lines
A
BC
Where is the Potential HighestA B C
A
BC
The Electric Field is the Slope of the Electric Potential
httpwwwfalstadcomvector3de
Ohms Law V = IR
Sources of Electric Potential Batteries
15 Volt Battery is the Voltage across the terminals
ExampleA 12V motorcycle battery moves 5000C of charge How much energy does it deliver to that charge
12V V=
0PE VqΔ = Δ
12 (5000 )V C=
12 (5000 )J C C=
4600 10x J=
Potential (Voltage) is NOT Energy
Positive Charges move from HI to LOW potential
HI V LOW V
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Equipotential Lines
A
BC
Where is the Potential HighestA B C
A
BC
The Electric Field is the Slope of the Electric Potential
httpwwwfalstadcomvector3de
Ohms Law V = IR
Sources of Electric Potential Batteries
15 Volt Battery is the Voltage across the terminals
ExampleA 12V motorcycle battery moves 5000C of charge How much energy does it deliver to that charge
12V V=
0PE VqΔ = Δ
12 (5000 )V C=
12 (5000 )J C C=
4600 10x J=
Potential (Voltage) is NOT Energy
Positive Charges move from HI to LOW potential
HI V LOW V
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Where is the Potential HighestA B C
A
BC
The Electric Field is the Slope of the Electric Potential
httpwwwfalstadcomvector3de
Ohms Law V = IR
Sources of Electric Potential Batteries
15 Volt Battery is the Voltage across the terminals
ExampleA 12V motorcycle battery moves 5000C of charge How much energy does it deliver to that charge
12V V=
0PE VqΔ = Δ
12 (5000 )V C=
12 (5000 )J C C=
4600 10x J=
Potential (Voltage) is NOT Energy
Positive Charges move from HI to LOW potential
HI V LOW V
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
The Electric Field is the Slope of the Electric Potential
httpwwwfalstadcomvector3de
Ohms Law V = IR
Sources of Electric Potential Batteries
15 Volt Battery is the Voltage across the terminals
ExampleA 12V motorcycle battery moves 5000C of charge How much energy does it deliver to that charge
12V V=
0PE VqΔ = Δ
12 (5000 )V C=
12 (5000 )J C C=
4600 10x J=
Potential (Voltage) is NOT Energy
Positive Charges move from HI to LOW potential
HI V LOW V
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
httpwwwfalstadcomvector3de
Ohms Law V = IR
Sources of Electric Potential Batteries
15 Volt Battery is the Voltage across the terminals
ExampleA 12V motorcycle battery moves 5000C of charge How much energy does it deliver to that charge
12V V=
0PE VqΔ = Δ
12 (5000 )V C=
12 (5000 )J C C=
4600 10x J=
Potential (Voltage) is NOT Energy
Positive Charges move from HI to LOW potential
HI V LOW V
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Ohms Law V = IR
Sources of Electric Potential Batteries
15 Volt Battery is the Voltage across the terminals
ExampleA 12V motorcycle battery moves 5000C of charge How much energy does it deliver to that charge
12V V=
0PE VqΔ = Δ
12 (5000 )V C=
12 (5000 )J C C=
4600 10x J=
Potential (Voltage) is NOT Energy
Positive Charges move from HI to LOW potential
HI V LOW V
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Sources of Electric Potential Batteries
15 Volt Battery is the Voltage across the terminals
ExampleA 12V motorcycle battery moves 5000C of charge How much energy does it deliver to that charge
12V V=
0PE VqΔ = Δ
12 (5000 )V C=
12 (5000 )J C C=
4600 10x J=
Potential (Voltage) is NOT Energy
Positive Charges move from HI to LOW potential
HI V LOW V
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
ExampleA 12V motorcycle battery moves 5000C of charge How much energy does it deliver to that charge
12V V=
0PE VqΔ = Δ
12 (5000 )V C=
12 (5000 )J C C=
4600 10x J=
Potential (Voltage) is NOT Energy
Positive Charges move from HI to LOW potential
HI V LOW V
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Positive Charges move from HI to LOW potential
HI V LOW V
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Negative Charges move from LOW to HI potential
HI V LOW V
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
HOW FAST DO ELECTRONS MOVE IN A CURRENTCARRYING CONDUCTING WIRE
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Electron Speed is called the DRIFT Velocity
Drift velocity ~ 001 ms
Electric Fields travel at the speed of light
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
bull Current flows from a higher potential to a lower potential (electrons flow the opposite way) Current carrying wires are neutral
bull DC current flows in one directionbull AC current oscillates back and forthbull Electrons have a drift velocity of 001ms bull Electric Fields travel at speed of light
I = Coulombsecond = Ampere
Current
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
ConductivityConductivitybull Conductors loosely bound electrons charge
flows freely Ex metals salt water
bull Insulators tightly bound electrons charge hard to move Ex organic materials wood glass water
bull Electrons move protons are bound in a latticebull Positively charged ions flow in fluid (liquid or gas)bull Positive amp Negative charges rearrange and become
Polarized in Insulators
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Resistance
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
bull The LONGER the wire the GREATER the Rbull The THINNER the wire the GREATER the Rbull The HOTTER the wire the GREATER the R
Resistance Resistivity
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
When are light bulbs more likely to blow
When hot or cold
The HOTTER the wire the GREATER the RAt lower Resistance the bulb draws more
current and it blows the filament
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Electrical Powerbull As a charge moves from a to b the
electric potential energy of the system increases by QΔV The chemical energy in the battery must decrease by this same amount
bull As the charge moves through the resistor (c to d) the system loses this electric potential energy during collisions of the electrons with the atoms of the resistor
bull This energy is transformed into internal energy in the resistor asincreased vibrational motion of the atoms in the resistor
P IV=
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
bull You pay for ENERGY not for ELECTRONSbull Kilowatt-hour is the energy consumed in one
hour [kWh]=J NOT TIME Power x Time
POWER P = IV[ ] WattEnergy JP
time s= = =
P IV=
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
QUESTION
The voltage and power on a light bulb read ldquo120 V 60 Wrdquo How much current will flow
through the bulb USE P = IV
I = PV = 60 W120 V = 12 Amp
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
QUESTION
The power and voltage on a light bulb read ldquo120 V 60 Wrdquo What is the resistance of the
filament (I = 5 A)Hint USE OHMS LAW V = IR
R = VI = 120 V 5 A = 240 Ω
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
If V = 120V What is I USE P = IV=gt I = PV
Appliance _ Power Current (A)
Hair Dryer 1600 Watts 133 A
Electric Iron 1200 Watts 10 A
TV 100 Watts 83 A
Computer 45 Watts 38 A
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts
Electric Iron 1200 Watts
TV 100 Watts
Computer 45 Watts
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Electric BillCost to run for 1 hr
$05 per 1 kw-hr Cost = Power x Time x Rate
Appliance _ Power Cost______
Hair Dryer 1600 Watts $008
Electric Iron 1200 Watts $006
TV 100 Watts $0005
Computer 45 Watts $0003
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
bull The current is the same in each devicebull The equivalent resistance of the circuit is the sum
of the individual resistances
bull The voltage of each device is the full voltage of the EMF source (the battery)
bull The total current is divided between each path
Parallel Circuits
Series Circuits
1 2
1 1 1
totalR R R= +
1 2totalR R R= +
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Circuits ProblemBulbs in Series vs ParallelA circuit contains a 48-V battery and two 240Ω light bulbs
In which circuit does each bulb burn brighterRULE THE MORE POWER DISSIPATED IN A BULB THE
BRIGHTER IT IS
P IV=Parallel Bulbs Burn Brighter
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Circuits ProblemBulbs in Series vs ParallelIf a bulb burns out - what happens to the other bulb in
each circuit Does it go out Is it brighter Dimmer Or
In the series circuit the burned out bulb will short the circuit and the other bulb will go out
In the parallel circuit the other bulb will have the same brightness
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Circuits Problem3 Bulbs in ParallelIf one more bulb is added to each circuit (3 bulbs total) how does the brightness of the bulbs change Or not
In the parallel circuit the bulbs DO NOT DIM WHY
In parallel each of the three equal bulbs gets the full voltage of the battery source
Is this getting something for nothing
NO Parallel circuits drain the battery faster
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Parallel CircuitsbullAs the number of branches is increased the overall resistance of the circuit is DECREASED
bullOverall resistance is lowered with each added path between any two points of the circuit
bullThis means the overall resistance of the circuit is less than the resistance of any one of the branches (Weird)
bullAs overall resistance is lowered more current is drawn This is how you blow fuses
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
QUESTION
The power rating for two light bulbs read30W and 60W Which bulb has the greatest
resistance at 120V 2 2 P V R R V P= rarr =
2(120 ) 30 480R V W= = Ω2(120 ) 60 240R V W= = Ω
(fyi Power ratings are for bulbs in parallel only)
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Ohmrsquos Law
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
War of Currents 1880rsquos
Thomas Edison American inventor and businessman pushed for the development of a DC power network
George WestinghouseAmerican entrepreneur and engineer backed financially the development of a practical AC power network
Nikola Tesla Serbian inventor physicist and electro-mechanical engineer was instrumental in developing AC networks
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
The first electric chair which was used to execute William Kemmler in 1890
Edison wired NYC with DC He carried out a campaign to discourage the use of AC including spreading information on fatal AC accidents killing animals and lobbying against the use of AC in state legislatures Edison opposed capital punishment but his desire to disparage the system of alternating current led to the invention of the electric chair Harold P Brown who was at this time being secretly paid by Edison constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC
Edisons Publicity Campaign
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
The first electric chair which was used to execute William Kemmler in 1890
Nebraska Only state that requires it 15-second-long jolt of 2450 volts of electricity (~ 8 Amps)
GE amp Edison We bring good things to lightMore than a 1000 killed since 1890
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow whether it uses alternating or direct current Ultimately the advantages of AC power transmission outweighed this theoretical risk and it was eventually adopted as the standard worldwide after Nikola Tesla designed the first AC hydroelectric power plant at Niagara Falls New York which started producing electrical power in 1895
Is AC Deadlier than DCThey are BOTH Deadly
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Electric Shock TherapyELECTRO CONVULSIVE
THERAPYAn electric shock is applied to produce a convulsive seizure
The shock is typically between 140 - 170 volts and lasts between 05 and 1 seconds No explanation of how it works
Used in the treatment of 1Chronic endogenous depression 2Bipolar disorder 3Acute mania 4Certain types of schizophrenia
In the US 33000 - 50000 people receive ECT each year
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Electric Shock
bullElectric Shock occurs when current is produced in the body which is caused by an impressed voltage
bullVoltage is the CAUSE bullCurrent does the DAMAGE
What causes electric Shock in the human body Voltage or Current
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Current (A) Effect
0001 Can be felt0005 Painful0010 Causes involuntary muscle spasms0015 Causes loss of muscle control0070 If through heart serious
If current lasts for 1 s - FATAL
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
Electric Shock
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Frequency Matters
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
Dry Skin Body Resistance 500000 ΩWet Skin Body Resistance 1000 Ω
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
QuestionWhat current would you draw if you were unfortunate to short-circuit a 120 V line with dry
hands Wet handsUse Ohmrsquos Law V = IR
DRY I = VR = 120 V500000 Ω = 00024 (live)
WET I = VR = 120 V1000 Ω = 12 (dead)
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
FusesIf the current drawn exceeds safe levels the fuse melts and the
circuit lsquobreaksrdquo ndash most house have switches not fuses
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Electrical Safety
Electrical Safety Grounding
Electrical Safety Grounding
Electrical Safety Grounding
Electrical Safety Grounding
Electrical Safety Grounding
