The value of workdone for rotating a magnet of magnetic moment M by an angle θ in external magnetic field H is given by

Options

(a) MH cos θ
(b) 2MH sin²(θ/2)
(c) MH sin θ
(d) MH (1-sin²θ)

Correct Answer:

MH cos θ

Explanation:

MH (1 – cos θ) = work done

.·. W = MH [1 – 1 + 2 sin² (θ / 2)] = 2MH sin² (θ / 2)