Electricity ppt presentation modified.pptx

8/12/2019 Electricity ppt presentation modified.pptx

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Electricity Theory

Ohms Law Combination of Resistors Electric Work & Power KirchhoffS Laws


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Potential Difference

Battery - Sorce of Emf


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Electric CurrentMovement of electric chargeRate of charge movement

QI

t

=unit Ampere, A

C1A=1 s


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Charge Movement

!ctal "low of Crrent


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Charge Movement

Con#entional "low of Crrent


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Types of CurrentAC Alternating current charges continuously

change direction forward and back at ! "#

$%ample& outlets (appro% '2! )

C irect current charges move in one direction

$%ample& batteries


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Ohms Law

Where$

% %olta'e (%)

* Crrent (!)

R Resistance ()

%

* R

*he ratio of potential difference (voltage) across a

conductor to the current it carries is constant which is the

resistance+


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ResistanceResistance is the impedance of the motion of chargethrough a conductor

VR

I

=

2

unit ohm,

V Js1 1 1

A C

= =


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Resistance *he electrical resistanceof a wire would be e%pected to

be greater for a longer wire, less for a wire of larger cross

sectional area, and would be e%pected to depend upon the

material out of which the wire is made+ $%perimentally,
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/resis.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/electric/resis.html


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Electric Power

Power& Rate at which work is done or Rate at which

energy is transformed

Electric Power& *he rate at which electricity does work orprovides energy+

ymbol - .unit watt, W

J1 W = 1

s


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Electrical Energy"ome use of electric energy is based on the amount of

$lectrical .ower use per hour

Measured in kilowatt hours

('!!! watts per hour) - k/h

E + P ,


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Resistor Combinations&

eries

.arallel

eries0parallel

Resistor CombinationsThe combination rules for any number of resistors in

series or parallel can be derived with the use of Ohms

Law the voltage law and the current law !


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"eries #esistors


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Parallel #esistors


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Kirchhoffs Laws

./ Kirchhoffs Point (or 0nction) Rle

01n any unction, the sum of all the currents coming into it must e3ual to

the sum of all the current leaving it+ (41 in - 4 1 out)

654321 IIIIII ++=++


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Kirchhoffs Laws2/ Kirchhoffs Loo1 (or circit) Rle

- *n any loo12 the al'ebraic sm of all emfs in it is e3al to the

al'ebraic sm of all the #olta'es or *R 4s 5ro1s in it/

= sIRsemf ''


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Definition of TermsLoo15 a closed conducting path

0nction5 a point where 6 or more resistances are

oined

Branch5 a conducting line connecting 2 unctions


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"ample Problems8+ A 6!0% and a +&-; connected series and the

combination is connected to a 27!0 dc line+ =ind& a) total

resistance of the combination b) total current drawn from the

source c) power dissipated by the combined resistors+

+ A 6!0; and a 2!0; connected parallel and the

combination is connected to a 27!0 dc line+ =ind& a) total

resistance of the combination b) total current drawn from thesource c) power dissipated by the combined resistors+


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Electricity ppt presentation modified.pptx