I was doing (ii) in the following question. The ESB supplies electrical energy at a rate of 2 MW to an industrial park from a local power station, whose output voltage is 10 kV. The total length of the cables connecting the industrial park to the power station is 15 km. The cables have a diameter of 10 mm and are made from a material of resistivity 5.0 × 10–8 Ω m. Calculate (i) the total resistance of the cables; (15) (ii) the current flowing in the cables; (6) (iii) the rate at which energy is “lost” in the cables. (6) Suggest a method of reducing the energy “lost” in the cables. (5) When trying to work out current I used V/R but from the marking scheme I found out that the right (and different) answer is obtained by using P/V. Are these two formula not equivalent? If not, what is different about them?