Question

The p.d. across a lamp is 12 V. How many joules of electrical energy are changed into heat and light when:
(a) a charge of 1 C passes through it?
(b) a charge of 5 C passes through it?
(c) a current of 2 A flows through it for 10 s?

Answer 1

Amount of energy = Work done
(a) Using the formula, V = W / Q, we have, W = V x Q
= 12 x 1 = 12 J

(b) W = V x Q = 12 x 5 = 60 J

(c) W = V x Q
= V x (I x t)
= 12 x 2 x 10 = 240 J