1. The problem statement, all variables and given/known data A small power plant produces a voltage of 6.0 kV and 150 A. The voltage is stepped up to 240 kV by the transformer before it is transmitted to a substation. The resistance of the transmission line between the power plants and the substation is 75 Ohms. What percentage of the power produced at the power plant is lost in the transmission of the substation? a) 0.47% b) 0.41% c) 0.34% d) 0.23% e) 0.12% (This is correct answer) 2. Relevant equations Ns/Np=Vs/Vp=Ip/Is P = IV P= I2R P = V2/R R = V/I 3. The attempt at a solution I know something is wrong with my attempt. The first thing I did was solve for the current of the line when the voltage is stepped up to 240 kV, which is 3.75 A compared to the 150 amps we started with. The problem I have now is with the resistance... If I use R = V/I then I can't get the current and volts to line up properly, and, in any event, the volts or currents I could get by fixing one of the numbers doesn't come out in a reasonable order of magnitude. For example, if I use 240 kV as my volts, then I get a current of 3200 A which is outlandish, so I must not be using this relationship properly. So I guess what I'm looking for is how do I quantify the effect of resistance on the line? Update: I found a way to get the answer, but I'm not sure why it should be this way... If I take the initial power at 9 * 105 by multiplying 6000 V by 150 A, and then I get a value of power in the line from the 3.75 amps as follows: P = (3.75)2(75 Ohms) = 1054 watts. If I take this number (1054W) not as the power in the line, but the power lost in the line, then I can subtract it from 9 * 105 and then simply generate a percent from the fierrence, giving me 0.12% My new question: Why in the world is P = I2R equal to the power lost in the line, and not simply the power in the line?