A circular loop of magnetic moment M is in an arbitrary orientation in an external magnetic field $\overrightarrow{B}$ . The work done to rotate the loop by $30^{\circ}$about an axis perpendicular to its plane is

Question

$\begin{array}{1 1} MB \\ \sqrt{3} \large\frac{MB}{2} \\ \large\frac{MB}{2} \\ zero \end{array}$

Comments

Why there is no change in the angle...plzz explain me