# Physics

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100000W of power is delivered to the other side of a city by a pair of power lines with the voltage difference of 15000V.

a) how much current flows in the lines?
100000/15000 = 6.9 A

b) Each of the 2 lines has a resistance of 10 ohms. What is the voltage change along each line?
6.9 x 10 = 69

c)How much power is wasted as heat in both lines together?

how on earth do you do part c ? help would be appreciated. thanks!

You punched a wrong button somewhere for 100,000/15,000. I have 6.67.

That slight difference will change answer b a little.

c. Power = I2R
Where I is current in amperes and R is resistance in ohms.

Thank you!

• Physics -

RIGHT, well this might be a bit late but i'm another physics student and just found the solution.

Basically you want to take your current from part A - and your resistance from part B, plug them in into the equation P = I^2R and then subtract your answer from the original power. i.e. 100kwatts

• Physics -

scratch that - no subtraction. just your answer as it is i think

• Physics -

i meant to say voltage and use the equation P = IV - then multiply by 2 since it's both lines KBAI

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