Question

The value of work done for rotating a magnet of magnetic moment $M$ by an angle $\theta$ with respect to magnetic field $B$ is given by :-

• A. $MB \cos \theta$
• B. $2 MB \sin ^{2} \frac{\theta}{2}$
• C. $MB \,\sin \theta$
• D. $MB(1-\sin \theta)$

Answer 1

Answer: (B)

$W=MB (1-\cos \theta)$
$= MB 2 \sin ^{2} \frac{\theta}{2}=2 MB \sin ^{2} \frac{\theta}{2}$
$=2 MB \sin ^{2} \frac{\theta}{2}$