Q.
A bar magnet of length ' $\ell$ ' and magnetic dipole moment '$M$' is bent in the form of an arc as shown in figure. The new magnetic dipole moment will be :-
Moving Charges and Magnetism
Solution:
$\frac{2 \pi r }{4}= L $
$\Rightarrow r =\frac{2 L }{\pi}$
$d =\sqrt{2} r =\frac{2 \sqrt{2 L }}{ \pi }$
$M _{\text {new }}=( M .d )$
$= mL \left\{\frac{2 \sqrt{2}}{\pi}\right\}=\frac{2 \sqrt{2} M }{\pi}$