Question: A thin circular disk of radius $R$ is uniformly charged with density $\sigma>0$ per unit area. The disk rotates about its axis with a uniform angular speed $\omega$. The magnetic moment of the disk is :-
$2 \pi R^{4} \sigma \omega$
$\pi R^{4} \sigma \omega$
$\frac{\pi \mathrm{R}^{4}}{2} \sigma \omega$
$\frac{\pi R^{4}}{4} \sigma \omega$
Correct Option: , 4
Solution:
