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 potential difference V = QV
i.e. W = QV
but = $\frac{Q}{t}$ = I Or Q = It
∴ W = VIt
Work done = Electrical energy

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

(b) Power ¡s the rate of doing W
P = $\frac{w}{t}$ = VI is the expression.