- #1

mer584

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## Homework Statement

A power station delivers 620kW of power at 12,000 V to a factory through wires with total resistance 3.0 ohms. How much less power is wasted if the electricity is delivered at 50,000V rather than 12,000V?

b]2. Homework Equations [/b]

P=IV=I^2R=V^2/R V=IR

## The Attempt at a Solution

So I know you need to find the current in order to be able to do this, but I'm a bit confused about when the different formulas for P can be used. The answer is 7500W.

I tried finding the current through the wire (12kV): 12kV = I(3 ohms) = 4000A

and the power lost to heat: (4000)^2 * 3 = 4.8 x 10^7 W

And the current through the wire (50kV): 50kV = I (3ohms) = 16666.67A

and the power lost to heat: (16666.67)^2 * 3 = 8.3 x 10^8 W

but these powers don't subtract to the answer. I'm not sure I understand the problem.