WAEC Physics 2017 Paper

Concept:For the same transmitted power, raising the voltage lowers the current, which reduces energy lost as heat in the wires.Explanation:The power transmitted is given by $P = VI$.So, if the voltage $V$ is increased, the current $I$ decreases while the same power is delivered.Heat lost in the transmission lines is $H = I^2Rt$.Since the heat loss depends on the square of the current, a small reduction in $I$ causes a large reduction in heat loss.Therefore, a.c. is transmitted at very high voltage and low current mainly to minimise heat loss.Answer:D. reduces heat loss