View
23
Download
0
Category
Preview:
DESCRIPTION
Chapter 6, Section 8. Energy Consumption: Cold Shower. HW: PTG 6.8 p 686 # 1-8, Due Friday. Learning Objective Calculate the energy efficiency of electrical devices. Success Criteria Calculate the heat gained by a sample of water. - PowerPoint PPT Presentation
Citation preview
Chapter 6 Section 8
Energy Consumption Cold Shower
HW PTG 68 p 686 1-8 Due Fridaybull Learning Objective
ndash Calculate the energy efficiency of electrical devices
bull Success Criteriandash Calculate the heat gained by a
sample of waterndash Calculate the electrical energy
converted into heat by a resistor
ndash Calculate the efficiency of a transformation of electrical energy to heat
ndash Explore the power ratings and energy consumption levels of a variety of electrical appliances
bull Do Nowndash 67 Quizndash LO and SC on new left
side pagendash WDYSWDYT p 678
bull Agendandash Do Nowndash Investigationndash Summary
What do you see
What do you thinkbull The entire daily energy output of a Homes
For Everyone (HFE) generator would not be enough to heat water for an average American family for a day
bull If an electrical heating coil (a type of resistor) were submerged in a container of water and if a current were to flow through the coil to make it hot what factors would affect the temperature increase of the water
Investigation 68bull 1 ndash setup and
measurements of water and coil
bull 2 Heat water for 10 minutes
bull While water heats set up notebook
Investigation 68bull Recall that the heat
gained by an object can be found using the equation
bull ΔQ = mcΔTndash ΔQ is a measure of heat in
joulesndash m is the mass of the
substance in gramsndash c is the specific heat of the
substance andndash ΔT is the change in
temperature in degrees Celsius
bull 3 ndash Calculate the heat gained using your data table and the specific heat value of418 JgdegC
Investigation 68bull P=Et so E=Ptbull where E is energy
in joules (watt-seconds)
bull P is power in watts (joulessecond)
bull t is time in seconds
bull 4 - Calculate the energy from your experiment using this equation
bull Answer 4 a and 5b
Investigation 68
100inputenergy
outputenergy useful Efficiency
bull 5 ndash Calculate the efficiency using the equation above and answer 5a
Summarybull Do you think the heated coil is very
efficient Why or why not Provide evidence to support your claim
HW PTG 68 p 686 1-8bull Learning Objective
ndash Calculate the energy efficiency of electrical devices
bull Success Criteriandash Calculate the heat gained by a
sample of waterndash Calculate the electrical energy
converted into heat by a resistor
ndash Calculate the efficiency of a transformation of electrical energy to heat
ndash Explore the power ratings and energy consumption levels of a variety of electrical appliances
bull Do Nowndash List some ways to
make the foam cup setup more energy efficient
bull Agendandash Do Nowndash Investigationndash Summary
Physics Talk 68bull What is a kilowatt-
hourbull 1 kilowatt-hour of
energy power timebull 1000W x 1 h = bull 1000W x 3600 sbull = 3600000 J
bull Thatrsquos a lot of joules
Physics Talk 68bull What is heat bull Heat is the transfer
of thermal energybull In order for an object
to heat up there must be a source of thermal energy
bull When objects cool down the thermal energy is being transferred elsewhere
Physics Talk 68bull How does a
thermos work bull A thermos creates a
barrier to isolate the contents This means that the amount of energy in the thermos must stay relatively the same
bull Cold things stay cold (blocks thermal energy from leaving)
bull Hot things stay hot (traps thermal energy in)
Physics Talk 68bull How do we
measure a change in heat
bull ΔQ = mcΔTndash ΔQ is a measure of
heat in joulesndash m is the mass of the
substance in gramsndash c is the specific
heat of the substance and
ndash ΔT is the change in temperature in degrees Celsius
Physics Talk 68bull Another method for calculating a change
in heatbull We know energy = power x timebull We also know power = voltage x currentbull This means energy = voltage x current x time
bull E = VItbull where E is the energy in joules (J)bull V is the voltage in volts (V)bull I is the current in amperes (A)bull t is the time in seconds (s)
Sample Problembull A 12-V starter
battery in a car supplies 48 A of current to the starter If the starter draws energy for 15 s how much energy does the starter use
bull Givenndash V = 12Vndash I = 48Andash t = 15s
bull Unknownndash Energy (E)
bull Toolndash E = VIt
bull Solutionndash E= 12V48A15sndash E = 8640 J
Canceling Units
Physics Talk 68bull What happened to
the missing energy in the experiment
bull Some of the heat could have been lost out of the cup into the thermometer or somewhere else The important thing is that it went somewhere because ENERGY IS NEVER DESTROYED
Physics Talk 68bull What is the equation for efficiency
100inputenergy
outputenergy useful Efficiency
Essential Questionsbull P 684 WDYTNbull Questions p 685ndash What does it meanndash How do you knowndash Why do you
believendash Why should you
care
Physics To Go 5-8 as a class
HW PTG 68 p 686 1-8 Due Fridaybull Learning Objective
ndash Calculate the energy efficiency of electrical devices
bull Success Criteriandash Calculate the heat gained by a
sample of waterndash Calculate the electrical energy
converted into heat by a resistor
ndash Calculate the efficiency of a transformation of electrical energy to heat
ndash Explore the power ratings and energy consumption levels of a variety of electrical appliances
bull Do Nowndash 67 Quizndash LO and SC on new left
side pagendash WDYSWDYT p 678
bull Agendandash Do Nowndash Investigationndash Summary
What do you see
What do you thinkbull The entire daily energy output of a Homes
For Everyone (HFE) generator would not be enough to heat water for an average American family for a day
bull If an electrical heating coil (a type of resistor) were submerged in a container of water and if a current were to flow through the coil to make it hot what factors would affect the temperature increase of the water
Investigation 68bull 1 ndash setup and
measurements of water and coil
bull 2 Heat water for 10 minutes
bull While water heats set up notebook
Investigation 68bull Recall that the heat
gained by an object can be found using the equation
bull ΔQ = mcΔTndash ΔQ is a measure of heat in
joulesndash m is the mass of the
substance in gramsndash c is the specific heat of the
substance andndash ΔT is the change in
temperature in degrees Celsius
bull 3 ndash Calculate the heat gained using your data table and the specific heat value of418 JgdegC
Investigation 68bull P=Et so E=Ptbull where E is energy
in joules (watt-seconds)
bull P is power in watts (joulessecond)
bull t is time in seconds
bull 4 - Calculate the energy from your experiment using this equation
bull Answer 4 a and 5b
Investigation 68
100inputenergy
outputenergy useful Efficiency
bull 5 ndash Calculate the efficiency using the equation above and answer 5a
Summarybull Do you think the heated coil is very
efficient Why or why not Provide evidence to support your claim
HW PTG 68 p 686 1-8bull Learning Objective
ndash Calculate the energy efficiency of electrical devices
bull Success Criteriandash Calculate the heat gained by a
sample of waterndash Calculate the electrical energy
converted into heat by a resistor
ndash Calculate the efficiency of a transformation of electrical energy to heat
ndash Explore the power ratings and energy consumption levels of a variety of electrical appliances
bull Do Nowndash List some ways to
make the foam cup setup more energy efficient
bull Agendandash Do Nowndash Investigationndash Summary
Physics Talk 68bull What is a kilowatt-
hourbull 1 kilowatt-hour of
energy power timebull 1000W x 1 h = bull 1000W x 3600 sbull = 3600000 J
bull Thatrsquos a lot of joules
Physics Talk 68bull What is heat bull Heat is the transfer
of thermal energybull In order for an object
to heat up there must be a source of thermal energy
bull When objects cool down the thermal energy is being transferred elsewhere
Physics Talk 68bull How does a
thermos work bull A thermos creates a
barrier to isolate the contents This means that the amount of energy in the thermos must stay relatively the same
bull Cold things stay cold (blocks thermal energy from leaving)
bull Hot things stay hot (traps thermal energy in)
Physics Talk 68bull How do we
measure a change in heat
bull ΔQ = mcΔTndash ΔQ is a measure of
heat in joulesndash m is the mass of the
substance in gramsndash c is the specific
heat of the substance and
ndash ΔT is the change in temperature in degrees Celsius
Physics Talk 68bull Another method for calculating a change
in heatbull We know energy = power x timebull We also know power = voltage x currentbull This means energy = voltage x current x time
bull E = VItbull where E is the energy in joules (J)bull V is the voltage in volts (V)bull I is the current in amperes (A)bull t is the time in seconds (s)
Sample Problembull A 12-V starter
battery in a car supplies 48 A of current to the starter If the starter draws energy for 15 s how much energy does the starter use
bull Givenndash V = 12Vndash I = 48Andash t = 15s
bull Unknownndash Energy (E)
bull Toolndash E = VIt
bull Solutionndash E= 12V48A15sndash E = 8640 J
Canceling Units
Physics Talk 68bull What happened to
the missing energy in the experiment
bull Some of the heat could have been lost out of the cup into the thermometer or somewhere else The important thing is that it went somewhere because ENERGY IS NEVER DESTROYED
Physics Talk 68bull What is the equation for efficiency
100inputenergy
outputenergy useful Efficiency
Essential Questionsbull P 684 WDYTNbull Questions p 685ndash What does it meanndash How do you knowndash Why do you
believendash Why should you
care
Physics To Go 5-8 as a class
What do you see
What do you thinkbull The entire daily energy output of a Homes
For Everyone (HFE) generator would not be enough to heat water for an average American family for a day
bull If an electrical heating coil (a type of resistor) were submerged in a container of water and if a current were to flow through the coil to make it hot what factors would affect the temperature increase of the water
Investigation 68bull 1 ndash setup and
measurements of water and coil
bull 2 Heat water for 10 minutes
bull While water heats set up notebook
Investigation 68bull Recall that the heat
gained by an object can be found using the equation
bull ΔQ = mcΔTndash ΔQ is a measure of heat in
joulesndash m is the mass of the
substance in gramsndash c is the specific heat of the
substance andndash ΔT is the change in
temperature in degrees Celsius
bull 3 ndash Calculate the heat gained using your data table and the specific heat value of418 JgdegC
Investigation 68bull P=Et so E=Ptbull where E is energy
in joules (watt-seconds)
bull P is power in watts (joulessecond)
bull t is time in seconds
bull 4 - Calculate the energy from your experiment using this equation
bull Answer 4 a and 5b
Investigation 68
100inputenergy
outputenergy useful Efficiency
bull 5 ndash Calculate the efficiency using the equation above and answer 5a
Summarybull Do you think the heated coil is very
efficient Why or why not Provide evidence to support your claim
HW PTG 68 p 686 1-8bull Learning Objective
ndash Calculate the energy efficiency of electrical devices
bull Success Criteriandash Calculate the heat gained by a
sample of waterndash Calculate the electrical energy
converted into heat by a resistor
ndash Calculate the efficiency of a transformation of electrical energy to heat
ndash Explore the power ratings and energy consumption levels of a variety of electrical appliances
bull Do Nowndash List some ways to
make the foam cup setup more energy efficient
bull Agendandash Do Nowndash Investigationndash Summary
Physics Talk 68bull What is a kilowatt-
hourbull 1 kilowatt-hour of
energy power timebull 1000W x 1 h = bull 1000W x 3600 sbull = 3600000 J
bull Thatrsquos a lot of joules
Physics Talk 68bull What is heat bull Heat is the transfer
of thermal energybull In order for an object
to heat up there must be a source of thermal energy
bull When objects cool down the thermal energy is being transferred elsewhere
Physics Talk 68bull How does a
thermos work bull A thermos creates a
barrier to isolate the contents This means that the amount of energy in the thermos must stay relatively the same
bull Cold things stay cold (blocks thermal energy from leaving)
bull Hot things stay hot (traps thermal energy in)
Physics Talk 68bull How do we
measure a change in heat
bull ΔQ = mcΔTndash ΔQ is a measure of
heat in joulesndash m is the mass of the
substance in gramsndash c is the specific
heat of the substance and
ndash ΔT is the change in temperature in degrees Celsius
Physics Talk 68bull Another method for calculating a change
in heatbull We know energy = power x timebull We also know power = voltage x currentbull This means energy = voltage x current x time
bull E = VItbull where E is the energy in joules (J)bull V is the voltage in volts (V)bull I is the current in amperes (A)bull t is the time in seconds (s)
Sample Problembull A 12-V starter
battery in a car supplies 48 A of current to the starter If the starter draws energy for 15 s how much energy does the starter use
bull Givenndash V = 12Vndash I = 48Andash t = 15s
bull Unknownndash Energy (E)
bull Toolndash E = VIt
bull Solutionndash E= 12V48A15sndash E = 8640 J
Canceling Units
Physics Talk 68bull What happened to
the missing energy in the experiment
bull Some of the heat could have been lost out of the cup into the thermometer or somewhere else The important thing is that it went somewhere because ENERGY IS NEVER DESTROYED
Physics Talk 68bull What is the equation for efficiency
100inputenergy
outputenergy useful Efficiency
Essential Questionsbull P 684 WDYTNbull Questions p 685ndash What does it meanndash How do you knowndash Why do you
believendash Why should you
care
Physics To Go 5-8 as a class
What do you thinkbull The entire daily energy output of a Homes
For Everyone (HFE) generator would not be enough to heat water for an average American family for a day
bull If an electrical heating coil (a type of resistor) were submerged in a container of water and if a current were to flow through the coil to make it hot what factors would affect the temperature increase of the water
Investigation 68bull 1 ndash setup and
measurements of water and coil
bull 2 Heat water for 10 minutes
bull While water heats set up notebook
Investigation 68bull Recall that the heat
gained by an object can be found using the equation
bull ΔQ = mcΔTndash ΔQ is a measure of heat in
joulesndash m is the mass of the
substance in gramsndash c is the specific heat of the
substance andndash ΔT is the change in
temperature in degrees Celsius
bull 3 ndash Calculate the heat gained using your data table and the specific heat value of418 JgdegC
Investigation 68bull P=Et so E=Ptbull where E is energy
in joules (watt-seconds)
bull P is power in watts (joulessecond)
bull t is time in seconds
bull 4 - Calculate the energy from your experiment using this equation
bull Answer 4 a and 5b
Investigation 68
100inputenergy
outputenergy useful Efficiency
bull 5 ndash Calculate the efficiency using the equation above and answer 5a
Summarybull Do you think the heated coil is very
efficient Why or why not Provide evidence to support your claim
HW PTG 68 p 686 1-8bull Learning Objective
ndash Calculate the energy efficiency of electrical devices
bull Success Criteriandash Calculate the heat gained by a
sample of waterndash Calculate the electrical energy
converted into heat by a resistor
ndash Calculate the efficiency of a transformation of electrical energy to heat
ndash Explore the power ratings and energy consumption levels of a variety of electrical appliances
bull Do Nowndash List some ways to
make the foam cup setup more energy efficient
bull Agendandash Do Nowndash Investigationndash Summary
Physics Talk 68bull What is a kilowatt-
hourbull 1 kilowatt-hour of
energy power timebull 1000W x 1 h = bull 1000W x 3600 sbull = 3600000 J
bull Thatrsquos a lot of joules
Physics Talk 68bull What is heat bull Heat is the transfer
of thermal energybull In order for an object
to heat up there must be a source of thermal energy
bull When objects cool down the thermal energy is being transferred elsewhere
Physics Talk 68bull How does a
thermos work bull A thermos creates a
barrier to isolate the contents This means that the amount of energy in the thermos must stay relatively the same
bull Cold things stay cold (blocks thermal energy from leaving)
bull Hot things stay hot (traps thermal energy in)
Physics Talk 68bull How do we
measure a change in heat
bull ΔQ = mcΔTndash ΔQ is a measure of
heat in joulesndash m is the mass of the
substance in gramsndash c is the specific
heat of the substance and
ndash ΔT is the change in temperature in degrees Celsius
Physics Talk 68bull Another method for calculating a change
in heatbull We know energy = power x timebull We also know power = voltage x currentbull This means energy = voltage x current x time
bull E = VItbull where E is the energy in joules (J)bull V is the voltage in volts (V)bull I is the current in amperes (A)bull t is the time in seconds (s)
Sample Problembull A 12-V starter
battery in a car supplies 48 A of current to the starter If the starter draws energy for 15 s how much energy does the starter use
bull Givenndash V = 12Vndash I = 48Andash t = 15s
bull Unknownndash Energy (E)
bull Toolndash E = VIt
bull Solutionndash E= 12V48A15sndash E = 8640 J
Canceling Units
Physics Talk 68bull What happened to
the missing energy in the experiment
bull Some of the heat could have been lost out of the cup into the thermometer or somewhere else The important thing is that it went somewhere because ENERGY IS NEVER DESTROYED
Physics Talk 68bull What is the equation for efficiency
100inputenergy
outputenergy useful Efficiency
Essential Questionsbull P 684 WDYTNbull Questions p 685ndash What does it meanndash How do you knowndash Why do you
believendash Why should you
care
Physics To Go 5-8 as a class
Investigation 68bull 1 ndash setup and
measurements of water and coil
bull 2 Heat water for 10 minutes
bull While water heats set up notebook
Investigation 68bull Recall that the heat
gained by an object can be found using the equation
bull ΔQ = mcΔTndash ΔQ is a measure of heat in
joulesndash m is the mass of the
substance in gramsndash c is the specific heat of the
substance andndash ΔT is the change in
temperature in degrees Celsius
bull 3 ndash Calculate the heat gained using your data table and the specific heat value of418 JgdegC
Investigation 68bull P=Et so E=Ptbull where E is energy
in joules (watt-seconds)
bull P is power in watts (joulessecond)
bull t is time in seconds
bull 4 - Calculate the energy from your experiment using this equation
bull Answer 4 a and 5b
Investigation 68
100inputenergy
outputenergy useful Efficiency
bull 5 ndash Calculate the efficiency using the equation above and answer 5a
Summarybull Do you think the heated coil is very
efficient Why or why not Provide evidence to support your claim
HW PTG 68 p 686 1-8bull Learning Objective
ndash Calculate the energy efficiency of electrical devices
bull Success Criteriandash Calculate the heat gained by a
sample of waterndash Calculate the electrical energy
converted into heat by a resistor
ndash Calculate the efficiency of a transformation of electrical energy to heat
ndash Explore the power ratings and energy consumption levels of a variety of electrical appliances
bull Do Nowndash List some ways to
make the foam cup setup more energy efficient
bull Agendandash Do Nowndash Investigationndash Summary
Physics Talk 68bull What is a kilowatt-
hourbull 1 kilowatt-hour of
energy power timebull 1000W x 1 h = bull 1000W x 3600 sbull = 3600000 J
bull Thatrsquos a lot of joules
Physics Talk 68bull What is heat bull Heat is the transfer
of thermal energybull In order for an object
to heat up there must be a source of thermal energy
bull When objects cool down the thermal energy is being transferred elsewhere
Physics Talk 68bull How does a
thermos work bull A thermos creates a
barrier to isolate the contents This means that the amount of energy in the thermos must stay relatively the same
bull Cold things stay cold (blocks thermal energy from leaving)
bull Hot things stay hot (traps thermal energy in)
Physics Talk 68bull How do we
measure a change in heat
bull ΔQ = mcΔTndash ΔQ is a measure of
heat in joulesndash m is the mass of the
substance in gramsndash c is the specific
heat of the substance and
ndash ΔT is the change in temperature in degrees Celsius
Physics Talk 68bull Another method for calculating a change
in heatbull We know energy = power x timebull We also know power = voltage x currentbull This means energy = voltage x current x time
bull E = VItbull where E is the energy in joules (J)bull V is the voltage in volts (V)bull I is the current in amperes (A)bull t is the time in seconds (s)
Sample Problembull A 12-V starter
battery in a car supplies 48 A of current to the starter If the starter draws energy for 15 s how much energy does the starter use
bull Givenndash V = 12Vndash I = 48Andash t = 15s
bull Unknownndash Energy (E)
bull Toolndash E = VIt
bull Solutionndash E= 12V48A15sndash E = 8640 J
Canceling Units
Physics Talk 68bull What happened to
the missing energy in the experiment
bull Some of the heat could have been lost out of the cup into the thermometer or somewhere else The important thing is that it went somewhere because ENERGY IS NEVER DESTROYED
Physics Talk 68bull What is the equation for efficiency
100inputenergy
outputenergy useful Efficiency
Essential Questionsbull P 684 WDYTNbull Questions p 685ndash What does it meanndash How do you knowndash Why do you
believendash Why should you
care
Physics To Go 5-8 as a class
Investigation 68bull Recall that the heat
gained by an object can be found using the equation
bull ΔQ = mcΔTndash ΔQ is a measure of heat in
joulesndash m is the mass of the
substance in gramsndash c is the specific heat of the
substance andndash ΔT is the change in
temperature in degrees Celsius
bull 3 ndash Calculate the heat gained using your data table and the specific heat value of418 JgdegC
Investigation 68bull P=Et so E=Ptbull where E is energy
in joules (watt-seconds)
bull P is power in watts (joulessecond)
bull t is time in seconds
bull 4 - Calculate the energy from your experiment using this equation
bull Answer 4 a and 5b
Investigation 68
100inputenergy
outputenergy useful Efficiency
bull 5 ndash Calculate the efficiency using the equation above and answer 5a
Summarybull Do you think the heated coil is very
efficient Why or why not Provide evidence to support your claim
HW PTG 68 p 686 1-8bull Learning Objective
ndash Calculate the energy efficiency of electrical devices
bull Success Criteriandash Calculate the heat gained by a
sample of waterndash Calculate the electrical energy
converted into heat by a resistor
ndash Calculate the efficiency of a transformation of electrical energy to heat
ndash Explore the power ratings and energy consumption levels of a variety of electrical appliances
bull Do Nowndash List some ways to
make the foam cup setup more energy efficient
bull Agendandash Do Nowndash Investigationndash Summary
Physics Talk 68bull What is a kilowatt-
hourbull 1 kilowatt-hour of
energy power timebull 1000W x 1 h = bull 1000W x 3600 sbull = 3600000 J
bull Thatrsquos a lot of joules
Physics Talk 68bull What is heat bull Heat is the transfer
of thermal energybull In order for an object
to heat up there must be a source of thermal energy
bull When objects cool down the thermal energy is being transferred elsewhere
Physics Talk 68bull How does a
thermos work bull A thermos creates a
barrier to isolate the contents This means that the amount of energy in the thermos must stay relatively the same
bull Cold things stay cold (blocks thermal energy from leaving)
bull Hot things stay hot (traps thermal energy in)
Physics Talk 68bull How do we
measure a change in heat
bull ΔQ = mcΔTndash ΔQ is a measure of
heat in joulesndash m is the mass of the
substance in gramsndash c is the specific
heat of the substance and
ndash ΔT is the change in temperature in degrees Celsius
Physics Talk 68bull Another method for calculating a change
in heatbull We know energy = power x timebull We also know power = voltage x currentbull This means energy = voltage x current x time
bull E = VItbull where E is the energy in joules (J)bull V is the voltage in volts (V)bull I is the current in amperes (A)bull t is the time in seconds (s)
Sample Problembull A 12-V starter
battery in a car supplies 48 A of current to the starter If the starter draws energy for 15 s how much energy does the starter use
bull Givenndash V = 12Vndash I = 48Andash t = 15s
bull Unknownndash Energy (E)
bull Toolndash E = VIt
bull Solutionndash E= 12V48A15sndash E = 8640 J
Canceling Units
Physics Talk 68bull What happened to
the missing energy in the experiment
bull Some of the heat could have been lost out of the cup into the thermometer or somewhere else The important thing is that it went somewhere because ENERGY IS NEVER DESTROYED
Physics Talk 68bull What is the equation for efficiency
100inputenergy
outputenergy useful Efficiency
Essential Questionsbull P 684 WDYTNbull Questions p 685ndash What does it meanndash How do you knowndash Why do you
believendash Why should you
care
Physics To Go 5-8 as a class
Investigation 68bull P=Et so E=Ptbull where E is energy
in joules (watt-seconds)
bull P is power in watts (joulessecond)
bull t is time in seconds
bull 4 - Calculate the energy from your experiment using this equation
bull Answer 4 a and 5b
Investigation 68
100inputenergy
outputenergy useful Efficiency
bull 5 ndash Calculate the efficiency using the equation above and answer 5a
Summarybull Do you think the heated coil is very
efficient Why or why not Provide evidence to support your claim
HW PTG 68 p 686 1-8bull Learning Objective
ndash Calculate the energy efficiency of electrical devices
bull Success Criteriandash Calculate the heat gained by a
sample of waterndash Calculate the electrical energy
converted into heat by a resistor
ndash Calculate the efficiency of a transformation of electrical energy to heat
ndash Explore the power ratings and energy consumption levels of a variety of electrical appliances
bull Do Nowndash List some ways to
make the foam cup setup more energy efficient
bull Agendandash Do Nowndash Investigationndash Summary
Physics Talk 68bull What is a kilowatt-
hourbull 1 kilowatt-hour of
energy power timebull 1000W x 1 h = bull 1000W x 3600 sbull = 3600000 J
bull Thatrsquos a lot of joules
Physics Talk 68bull What is heat bull Heat is the transfer
of thermal energybull In order for an object
to heat up there must be a source of thermal energy
bull When objects cool down the thermal energy is being transferred elsewhere
Physics Talk 68bull How does a
thermos work bull A thermos creates a
barrier to isolate the contents This means that the amount of energy in the thermos must stay relatively the same
bull Cold things stay cold (blocks thermal energy from leaving)
bull Hot things stay hot (traps thermal energy in)
Physics Talk 68bull How do we
measure a change in heat
bull ΔQ = mcΔTndash ΔQ is a measure of
heat in joulesndash m is the mass of the
substance in gramsndash c is the specific
heat of the substance and
ndash ΔT is the change in temperature in degrees Celsius
Physics Talk 68bull Another method for calculating a change
in heatbull We know energy = power x timebull We also know power = voltage x currentbull This means energy = voltage x current x time
bull E = VItbull where E is the energy in joules (J)bull V is the voltage in volts (V)bull I is the current in amperes (A)bull t is the time in seconds (s)
Sample Problembull A 12-V starter
battery in a car supplies 48 A of current to the starter If the starter draws energy for 15 s how much energy does the starter use
bull Givenndash V = 12Vndash I = 48Andash t = 15s
bull Unknownndash Energy (E)
bull Toolndash E = VIt
bull Solutionndash E= 12V48A15sndash E = 8640 J
Canceling Units
Physics Talk 68bull What happened to
the missing energy in the experiment
bull Some of the heat could have been lost out of the cup into the thermometer or somewhere else The important thing is that it went somewhere because ENERGY IS NEVER DESTROYED
Physics Talk 68bull What is the equation for efficiency
100inputenergy
outputenergy useful Efficiency
Essential Questionsbull P 684 WDYTNbull Questions p 685ndash What does it meanndash How do you knowndash Why do you
believendash Why should you
care
Physics To Go 5-8 as a class
Investigation 68
100inputenergy
outputenergy useful Efficiency
bull 5 ndash Calculate the efficiency using the equation above and answer 5a
Summarybull Do you think the heated coil is very
efficient Why or why not Provide evidence to support your claim
HW PTG 68 p 686 1-8bull Learning Objective
ndash Calculate the energy efficiency of electrical devices
bull Success Criteriandash Calculate the heat gained by a
sample of waterndash Calculate the electrical energy
converted into heat by a resistor
ndash Calculate the efficiency of a transformation of electrical energy to heat
ndash Explore the power ratings and energy consumption levels of a variety of electrical appliances
bull Do Nowndash List some ways to
make the foam cup setup more energy efficient
bull Agendandash Do Nowndash Investigationndash Summary
Physics Talk 68bull What is a kilowatt-
hourbull 1 kilowatt-hour of
energy power timebull 1000W x 1 h = bull 1000W x 3600 sbull = 3600000 J
bull Thatrsquos a lot of joules
Physics Talk 68bull What is heat bull Heat is the transfer
of thermal energybull In order for an object
to heat up there must be a source of thermal energy
bull When objects cool down the thermal energy is being transferred elsewhere
Physics Talk 68bull How does a
thermos work bull A thermos creates a
barrier to isolate the contents This means that the amount of energy in the thermos must stay relatively the same
bull Cold things stay cold (blocks thermal energy from leaving)
bull Hot things stay hot (traps thermal energy in)
Physics Talk 68bull How do we
measure a change in heat
bull ΔQ = mcΔTndash ΔQ is a measure of
heat in joulesndash m is the mass of the
substance in gramsndash c is the specific
heat of the substance and
ndash ΔT is the change in temperature in degrees Celsius
Physics Talk 68bull Another method for calculating a change
in heatbull We know energy = power x timebull We also know power = voltage x currentbull This means energy = voltage x current x time
bull E = VItbull where E is the energy in joules (J)bull V is the voltage in volts (V)bull I is the current in amperes (A)bull t is the time in seconds (s)
Sample Problembull A 12-V starter
battery in a car supplies 48 A of current to the starter If the starter draws energy for 15 s how much energy does the starter use
bull Givenndash V = 12Vndash I = 48Andash t = 15s
bull Unknownndash Energy (E)
bull Toolndash E = VIt
bull Solutionndash E= 12V48A15sndash E = 8640 J
Canceling Units
Physics Talk 68bull What happened to
the missing energy in the experiment
bull Some of the heat could have been lost out of the cup into the thermometer or somewhere else The important thing is that it went somewhere because ENERGY IS NEVER DESTROYED
Physics Talk 68bull What is the equation for efficiency
100inputenergy
outputenergy useful Efficiency
Essential Questionsbull P 684 WDYTNbull Questions p 685ndash What does it meanndash How do you knowndash Why do you
believendash Why should you
care
Physics To Go 5-8 as a class
Summarybull Do you think the heated coil is very
efficient Why or why not Provide evidence to support your claim
HW PTG 68 p 686 1-8bull Learning Objective
ndash Calculate the energy efficiency of electrical devices
bull Success Criteriandash Calculate the heat gained by a
sample of waterndash Calculate the electrical energy
converted into heat by a resistor
ndash Calculate the efficiency of a transformation of electrical energy to heat
ndash Explore the power ratings and energy consumption levels of a variety of electrical appliances
bull Do Nowndash List some ways to
make the foam cup setup more energy efficient
bull Agendandash Do Nowndash Investigationndash Summary
Physics Talk 68bull What is a kilowatt-
hourbull 1 kilowatt-hour of
energy power timebull 1000W x 1 h = bull 1000W x 3600 sbull = 3600000 J
bull Thatrsquos a lot of joules
Physics Talk 68bull What is heat bull Heat is the transfer
of thermal energybull In order for an object
to heat up there must be a source of thermal energy
bull When objects cool down the thermal energy is being transferred elsewhere
Physics Talk 68bull How does a
thermos work bull A thermos creates a
barrier to isolate the contents This means that the amount of energy in the thermos must stay relatively the same
bull Cold things stay cold (blocks thermal energy from leaving)
bull Hot things stay hot (traps thermal energy in)
Physics Talk 68bull How do we
measure a change in heat
bull ΔQ = mcΔTndash ΔQ is a measure of
heat in joulesndash m is the mass of the
substance in gramsndash c is the specific
heat of the substance and
ndash ΔT is the change in temperature in degrees Celsius
Physics Talk 68bull Another method for calculating a change
in heatbull We know energy = power x timebull We also know power = voltage x currentbull This means energy = voltage x current x time
bull E = VItbull where E is the energy in joules (J)bull V is the voltage in volts (V)bull I is the current in amperes (A)bull t is the time in seconds (s)
Sample Problembull A 12-V starter
battery in a car supplies 48 A of current to the starter If the starter draws energy for 15 s how much energy does the starter use
bull Givenndash V = 12Vndash I = 48Andash t = 15s
bull Unknownndash Energy (E)
bull Toolndash E = VIt
bull Solutionndash E= 12V48A15sndash E = 8640 J
Canceling Units
Physics Talk 68bull What happened to
the missing energy in the experiment
bull Some of the heat could have been lost out of the cup into the thermometer or somewhere else The important thing is that it went somewhere because ENERGY IS NEVER DESTROYED
Physics Talk 68bull What is the equation for efficiency
100inputenergy
outputenergy useful Efficiency
Essential Questionsbull P 684 WDYTNbull Questions p 685ndash What does it meanndash How do you knowndash Why do you
believendash Why should you
care
Physics To Go 5-8 as a class
HW PTG 68 p 686 1-8bull Learning Objective
ndash Calculate the energy efficiency of electrical devices
bull Success Criteriandash Calculate the heat gained by a
sample of waterndash Calculate the electrical energy
converted into heat by a resistor
ndash Calculate the efficiency of a transformation of electrical energy to heat
ndash Explore the power ratings and energy consumption levels of a variety of electrical appliances
bull Do Nowndash List some ways to
make the foam cup setup more energy efficient
bull Agendandash Do Nowndash Investigationndash Summary
Physics Talk 68bull What is a kilowatt-
hourbull 1 kilowatt-hour of
energy power timebull 1000W x 1 h = bull 1000W x 3600 sbull = 3600000 J
bull Thatrsquos a lot of joules
Physics Talk 68bull What is heat bull Heat is the transfer
of thermal energybull In order for an object
to heat up there must be a source of thermal energy
bull When objects cool down the thermal energy is being transferred elsewhere
Physics Talk 68bull How does a
thermos work bull A thermos creates a
barrier to isolate the contents This means that the amount of energy in the thermos must stay relatively the same
bull Cold things stay cold (blocks thermal energy from leaving)
bull Hot things stay hot (traps thermal energy in)
Physics Talk 68bull How do we
measure a change in heat
bull ΔQ = mcΔTndash ΔQ is a measure of
heat in joulesndash m is the mass of the
substance in gramsndash c is the specific
heat of the substance and
ndash ΔT is the change in temperature in degrees Celsius
Physics Talk 68bull Another method for calculating a change
in heatbull We know energy = power x timebull We also know power = voltage x currentbull This means energy = voltage x current x time
bull E = VItbull where E is the energy in joules (J)bull V is the voltage in volts (V)bull I is the current in amperes (A)bull t is the time in seconds (s)
Sample Problembull A 12-V starter
battery in a car supplies 48 A of current to the starter If the starter draws energy for 15 s how much energy does the starter use
bull Givenndash V = 12Vndash I = 48Andash t = 15s
bull Unknownndash Energy (E)
bull Toolndash E = VIt
bull Solutionndash E= 12V48A15sndash E = 8640 J
Canceling Units
Physics Talk 68bull What happened to
the missing energy in the experiment
bull Some of the heat could have been lost out of the cup into the thermometer or somewhere else The important thing is that it went somewhere because ENERGY IS NEVER DESTROYED
Physics Talk 68bull What is the equation for efficiency
100inputenergy
outputenergy useful Efficiency
Essential Questionsbull P 684 WDYTNbull Questions p 685ndash What does it meanndash How do you knowndash Why do you
believendash Why should you
care
Physics To Go 5-8 as a class
Physics Talk 68bull What is a kilowatt-
hourbull 1 kilowatt-hour of
energy power timebull 1000W x 1 h = bull 1000W x 3600 sbull = 3600000 J
bull Thatrsquos a lot of joules
Physics Talk 68bull What is heat bull Heat is the transfer
of thermal energybull In order for an object
to heat up there must be a source of thermal energy
bull When objects cool down the thermal energy is being transferred elsewhere
Physics Talk 68bull How does a
thermos work bull A thermos creates a
barrier to isolate the contents This means that the amount of energy in the thermos must stay relatively the same
bull Cold things stay cold (blocks thermal energy from leaving)
bull Hot things stay hot (traps thermal energy in)
Physics Talk 68bull How do we
measure a change in heat
bull ΔQ = mcΔTndash ΔQ is a measure of
heat in joulesndash m is the mass of the
substance in gramsndash c is the specific
heat of the substance and
ndash ΔT is the change in temperature in degrees Celsius
Physics Talk 68bull Another method for calculating a change
in heatbull We know energy = power x timebull We also know power = voltage x currentbull This means energy = voltage x current x time
bull E = VItbull where E is the energy in joules (J)bull V is the voltage in volts (V)bull I is the current in amperes (A)bull t is the time in seconds (s)
Sample Problembull A 12-V starter
battery in a car supplies 48 A of current to the starter If the starter draws energy for 15 s how much energy does the starter use
bull Givenndash V = 12Vndash I = 48Andash t = 15s
bull Unknownndash Energy (E)
bull Toolndash E = VIt
bull Solutionndash E= 12V48A15sndash E = 8640 J
Canceling Units
Physics Talk 68bull What happened to
the missing energy in the experiment
bull Some of the heat could have been lost out of the cup into the thermometer or somewhere else The important thing is that it went somewhere because ENERGY IS NEVER DESTROYED
Physics Talk 68bull What is the equation for efficiency
100inputenergy
outputenergy useful Efficiency
Essential Questionsbull P 684 WDYTNbull Questions p 685ndash What does it meanndash How do you knowndash Why do you
believendash Why should you
care
Physics To Go 5-8 as a class
Physics Talk 68bull What is heat bull Heat is the transfer
of thermal energybull In order for an object
to heat up there must be a source of thermal energy
bull When objects cool down the thermal energy is being transferred elsewhere
Physics Talk 68bull How does a
thermos work bull A thermos creates a
barrier to isolate the contents This means that the amount of energy in the thermos must stay relatively the same
bull Cold things stay cold (blocks thermal energy from leaving)
bull Hot things stay hot (traps thermal energy in)
Physics Talk 68bull How do we
measure a change in heat
bull ΔQ = mcΔTndash ΔQ is a measure of
heat in joulesndash m is the mass of the
substance in gramsndash c is the specific
heat of the substance and
ndash ΔT is the change in temperature in degrees Celsius
Physics Talk 68bull Another method for calculating a change
in heatbull We know energy = power x timebull We also know power = voltage x currentbull This means energy = voltage x current x time
bull E = VItbull where E is the energy in joules (J)bull V is the voltage in volts (V)bull I is the current in amperes (A)bull t is the time in seconds (s)
Sample Problembull A 12-V starter
battery in a car supplies 48 A of current to the starter If the starter draws energy for 15 s how much energy does the starter use
bull Givenndash V = 12Vndash I = 48Andash t = 15s
bull Unknownndash Energy (E)
bull Toolndash E = VIt
bull Solutionndash E= 12V48A15sndash E = 8640 J
Canceling Units
Physics Talk 68bull What happened to
the missing energy in the experiment
bull Some of the heat could have been lost out of the cup into the thermometer or somewhere else The important thing is that it went somewhere because ENERGY IS NEVER DESTROYED
Physics Talk 68bull What is the equation for efficiency
100inputenergy
outputenergy useful Efficiency
Essential Questionsbull P 684 WDYTNbull Questions p 685ndash What does it meanndash How do you knowndash Why do you
believendash Why should you
care
Physics To Go 5-8 as a class
Physics Talk 68bull How does a
thermos work bull A thermos creates a
barrier to isolate the contents This means that the amount of energy in the thermos must stay relatively the same
bull Cold things stay cold (blocks thermal energy from leaving)
bull Hot things stay hot (traps thermal energy in)
Physics Talk 68bull How do we
measure a change in heat
bull ΔQ = mcΔTndash ΔQ is a measure of
heat in joulesndash m is the mass of the
substance in gramsndash c is the specific
heat of the substance and
ndash ΔT is the change in temperature in degrees Celsius
Physics Talk 68bull Another method for calculating a change
in heatbull We know energy = power x timebull We also know power = voltage x currentbull This means energy = voltage x current x time
bull E = VItbull where E is the energy in joules (J)bull V is the voltage in volts (V)bull I is the current in amperes (A)bull t is the time in seconds (s)
Sample Problembull A 12-V starter
battery in a car supplies 48 A of current to the starter If the starter draws energy for 15 s how much energy does the starter use
bull Givenndash V = 12Vndash I = 48Andash t = 15s
bull Unknownndash Energy (E)
bull Toolndash E = VIt
bull Solutionndash E= 12V48A15sndash E = 8640 J
Canceling Units
Physics Talk 68bull What happened to
the missing energy in the experiment
bull Some of the heat could have been lost out of the cup into the thermometer or somewhere else The important thing is that it went somewhere because ENERGY IS NEVER DESTROYED
Physics Talk 68bull What is the equation for efficiency
100inputenergy
outputenergy useful Efficiency
Essential Questionsbull P 684 WDYTNbull Questions p 685ndash What does it meanndash How do you knowndash Why do you
believendash Why should you
care
Physics To Go 5-8 as a class
Physics Talk 68bull How do we
measure a change in heat
bull ΔQ = mcΔTndash ΔQ is a measure of
heat in joulesndash m is the mass of the
substance in gramsndash c is the specific
heat of the substance and
ndash ΔT is the change in temperature in degrees Celsius
Physics Talk 68bull Another method for calculating a change
in heatbull We know energy = power x timebull We also know power = voltage x currentbull This means energy = voltage x current x time
bull E = VItbull where E is the energy in joules (J)bull V is the voltage in volts (V)bull I is the current in amperes (A)bull t is the time in seconds (s)
Sample Problembull A 12-V starter
battery in a car supplies 48 A of current to the starter If the starter draws energy for 15 s how much energy does the starter use
bull Givenndash V = 12Vndash I = 48Andash t = 15s
bull Unknownndash Energy (E)
bull Toolndash E = VIt
bull Solutionndash E= 12V48A15sndash E = 8640 J
Canceling Units
Physics Talk 68bull What happened to
the missing energy in the experiment
bull Some of the heat could have been lost out of the cup into the thermometer or somewhere else The important thing is that it went somewhere because ENERGY IS NEVER DESTROYED
Physics Talk 68bull What is the equation for efficiency
100inputenergy
outputenergy useful Efficiency
Essential Questionsbull P 684 WDYTNbull Questions p 685ndash What does it meanndash How do you knowndash Why do you
believendash Why should you
care
Physics To Go 5-8 as a class
Physics Talk 68bull Another method for calculating a change
in heatbull We know energy = power x timebull We also know power = voltage x currentbull This means energy = voltage x current x time
bull E = VItbull where E is the energy in joules (J)bull V is the voltage in volts (V)bull I is the current in amperes (A)bull t is the time in seconds (s)
Sample Problembull A 12-V starter
battery in a car supplies 48 A of current to the starter If the starter draws energy for 15 s how much energy does the starter use
bull Givenndash V = 12Vndash I = 48Andash t = 15s
bull Unknownndash Energy (E)
bull Toolndash E = VIt
bull Solutionndash E= 12V48A15sndash E = 8640 J
Canceling Units
Physics Talk 68bull What happened to
the missing energy in the experiment
bull Some of the heat could have been lost out of the cup into the thermometer or somewhere else The important thing is that it went somewhere because ENERGY IS NEVER DESTROYED
Physics Talk 68bull What is the equation for efficiency
100inputenergy
outputenergy useful Efficiency
Essential Questionsbull P 684 WDYTNbull Questions p 685ndash What does it meanndash How do you knowndash Why do you
believendash Why should you
care
Physics To Go 5-8 as a class
Sample Problembull A 12-V starter
battery in a car supplies 48 A of current to the starter If the starter draws energy for 15 s how much energy does the starter use
bull Givenndash V = 12Vndash I = 48Andash t = 15s
bull Unknownndash Energy (E)
bull Toolndash E = VIt
bull Solutionndash E= 12V48A15sndash E = 8640 J
Canceling Units
Physics Talk 68bull What happened to
the missing energy in the experiment
bull Some of the heat could have been lost out of the cup into the thermometer or somewhere else The important thing is that it went somewhere because ENERGY IS NEVER DESTROYED
Physics Talk 68bull What is the equation for efficiency
100inputenergy
outputenergy useful Efficiency
Essential Questionsbull P 684 WDYTNbull Questions p 685ndash What does it meanndash How do you knowndash Why do you
believendash Why should you
care
Physics To Go 5-8 as a class
Canceling Units
Physics Talk 68bull What happened to
the missing energy in the experiment
bull Some of the heat could have been lost out of the cup into the thermometer or somewhere else The important thing is that it went somewhere because ENERGY IS NEVER DESTROYED
Physics Talk 68bull What is the equation for efficiency
100inputenergy
outputenergy useful Efficiency
Essential Questionsbull P 684 WDYTNbull Questions p 685ndash What does it meanndash How do you knowndash Why do you
believendash Why should you
care
Physics To Go 5-8 as a class
Physics Talk 68bull What happened to
the missing energy in the experiment
bull Some of the heat could have been lost out of the cup into the thermometer or somewhere else The important thing is that it went somewhere because ENERGY IS NEVER DESTROYED
Physics Talk 68bull What is the equation for efficiency
100inputenergy
outputenergy useful Efficiency
Essential Questionsbull P 684 WDYTNbull Questions p 685ndash What does it meanndash How do you knowndash Why do you
believendash Why should you
care
Physics To Go 5-8 as a class
Physics Talk 68bull What is the equation for efficiency
100inputenergy
outputenergy useful Efficiency
Essential Questionsbull P 684 WDYTNbull Questions p 685ndash What does it meanndash How do you knowndash Why do you
believendash Why should you
care
Physics To Go 5-8 as a class
Essential Questionsbull P 684 WDYTNbull Questions p 685ndash What does it meanndash How do you knowndash Why do you
believendash Why should you
care
Physics To Go 5-8 as a class
Physics To Go 5-8 as a class
Recommended