Question

A bar magnet is free to vibrate in a horizontal plane. At the magnetic equator, the time period of oscillations is found out to be equal to $T$. What will be its time period of oscillations on one of the magnetic poles of earth?

• A. $T$
• B. $\frac{T}{2}$
• C. $2T$
• D. infinity

Answer 1

The correct option is D infinity

At magnetic equator,

$T=2\pi \sqrt{\frac{I}{MB}}(\because B=B_H)$

As the bar magnet can rotate only in horizontal plane, and at poles $B_H=0$, so the time period of magnet will be infinity i.e. cannot be defined.

Hence, option $\left(D\right)$ is the correct answer.