Series, Parallel Differences
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III) Electric Power
Power - time rate of doing work or expending energy
| P = W/t | |
| (watts) | (J/seconds) |
since V = W/q,
CROSS MULTIPLY
then W = Vq
P = Vq/t
| P = VI |
(All equations in reference table)
P = VI since V = IR …
THEN P = I2R
since I = V/R …
THEN P = V2/R
P = VI = I2R = V2/R
P = W/t
Giancoli p. 516) 11
a) R = 20. ohms
P = W/t = VI
W = VIt
= 12V[.60 A]60 sec
b) 430 J
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Ex) A series circuit contains two lamps and a battery with a potential difference of 1.5 volts. If the current in the circuit is 0.10 ampere, at what rate does the circuit use energy? |
Ex) Series circuit w/ two lamps, the battery supplies a potential difference of 1.5 volts. Current in the circuit is 0.10 ampere, what rate does the circuit use energy?
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| a)15 W | b)1.5 W | d).15 W | c).015W |
V = 1.5 V
I = .10 Amps
P = ?
(rate of energy use)
P = VI = 1.5 V(.10 A)
P = .15 watts
or .15 VA
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P, R Relationship????
P = I2R = V2/R
P,R direct when resistors have same current P = I2R P,R Inverse when resistors have same V P = V2/R |
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In which kind of circuit would a 5 Ω resistor be brighter (more power) than a 10 Ω resistor?
(Hint: P = V2/R and P = I2R)
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Parallel Circuit, P = V2/R
P, R are inverse when
V is constant.
5 Ω would be brighter because it has less R
Review - Series or Parallel?
Dorling Kindersley Books
Parallel
AP Physics
p. 517) 33, 35, 37 |
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