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Question about voltage and power change along each line.?
100 kW (10^5 W) of power is delivered to the other side of a city by a pair of powerlines, between which the voltage is 12,000 V.
(a) What current flows in the lines? (b) Each of the two lines has a resistance of 10 ohms. What is the voltage change along each line? (This voltage change is along each line, not between the lines) (c) What power is expended as heat in both lines together (distinct from power delivered to customers)?
for (a), I know the formula for current is I = V/R ; therefore, I got I = 12,000/10 ... and I got 1200 A for the current.
1 Answer
- Letao12Lv 41 decade agoFavorite Answer
a) I = V/R doesn't work here, because the V given is not the voltage along one wire (that's part b). Instead, use
I = P / V = 100000 W / 12000 V = 8.33 A.
b) Here's where V = I R works.
V = 8.33 A * 10 ohm = 83.3 V
c) Use either P = I V or P = V^2 / R or P = I^2 * R, they will all give the same answer.
P = I V = 8.33 A * 83.3 V * 2 wires = 1389 W
