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Unformatted text preview: Summary Lecture 7
Ohm’s Law
V = ItotRtot
Series Circuits
Circuits
current is the same
through all elements
Itot = I1 = I2
V = V1 + V2
R = R 1 + R2
V1 = Itot R1 = R1/Rtot V
V2 = Itot R2 = R2/Rtot V R1
V
R2 Parallel Circuits
Circuits
same voltage across
all elements
elements
V = V1 = V2
Itot = I1 + I2
1/R = 1/R1 + 1/R2
I1 = V / R1
I2 = V / R2 V R1 R2 Electric Power and Energy
Electric potential Energy:
PE = Q V
Using the definition of current I = Q/t
the definition of current
Q/t
(Electric) Energy = VIt Power = Energy transformed
time PE = V Q
P=
t
t =VI P = VI = RI2 = V2/R
VI RI
Power lost in a wire: PLost = RI2
lost in wire:
RI
Energy = Power x Time = VIt [kWh] 4Resistor Circuit
V = 10.0 V
R1 = 100 R3 = 60 R2 = 30 R4 = 25 R1 R4 V R2 Questions:
• What is I1, the current through R1?
• What is Rtot (Rs)
• What is V2 and I2? R3 ...
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 Spring '11
 Beacom
 Physics, Current

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