Question

A source of potential difference V volt sends current I ampere in a circuit for time t second. Write expressions for

(a) electrical energy supplied by the source, and

(b) electrical power spent by the source.

Answer 1

Potential difference V is the work done in moving a unit charge

∴ Work done in moving a charge Q through pot. diff. V = QV

i.e. W = QV

but = Q / t = I Or Q = It

∴ W = VIt

Work done = Electrical energy

(a) :. Electrical energy = VIt is the expression

(b) Power is the rate of doing W

P = W/t = VIt/t = VI

P = VI is the expression.