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*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)

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?