Q. A magnet of magnetic moment $M$ oscillating freely in earth’s horizontal magnetic field makes $n$ oscillations per minute. If the magnetic moment is quadrupled and the earth’s field is doubled, the number of oscillations made per minute would be
A) $\frac{n}{2\sqrt{2}}$
B) $\frac{n}{\sqrt{2}}$
C) $2\sqrt{2}n$
D) $\sqrt{2}n$
Explanation
(c) No. of oscillation per minute $= \frac{1}{2\pi}\sqrt{\frac{MB_{H}}{I}}$
$\Rightarrow n \propto \sqrt{MB_{H}};M \rightarrow 4\ times$
$B_{H} \rightarrow 2\ times$
So $v \rightarrow \sqrt{8}\ times\ i.e.\ v^{'} = \sqrt{8}v = 2\sqrt{2}n$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.