1. The problem statement, all variables and given/known data In Australia, New South Wale's final year of high school, a common question is asking something like: How does distributing electricity at high voltages reduce power loss in the transmission lines. 2. Relevant equations P = VI = (I^2)R = (V^2)/R. Not very clear without subscripts. 3. The attempt at a solution I attached an image http://imageshack.us/f/16/image0001lmg.jpg/ R_wire is the resistance of the transmission lines R_load is the load All the textbooks and teachers will teach it as shown in Case1 which essentially says: P_input = V_supply * I = constant If we distribute at high V_supply, current I must fall (since P_input is constant). Since current I falls, P_loss = I^2 * R_wire must also fall. But what about Case 2? Using P_loss = V_wire^2/R_wire seems to end up with a contradictory result.