question_answer 53)

  1 MW power is to be delivered from a power station to a town 10 km away. One uses a pair of Cu wires of radius  cm for this purpose. Calculate the fraction of ohmic losses to power transmitted if (i) power is transmitted at 220 V. Comment on the feasibility of doing this. (ii) a step-up transformer is used to boost the voltage to 11000 V, power transmitted, then a step-down transformer is used to bring voltage to 220 V.

Answer:

                  (i) As the town is 10 km away, length of pair of Cu-wires used,  = 20 km = 20000 m. Resistance of wires, When power P =  watt is transmitted at V = 220 V. Current drawn, Power loss,          which is so large. Therefore, this method of transmission of power is not feasible. (ii) When power P = watt is transmitted at 11000 V, Current drawn,   Power loss, Fraction of ohmic losses to power transmitted.