Question

A bar magnet is oscillating in earth's magnetic field with periodic time $T$. If a similar magnet with the same mass and volume has magnetic dipole moment, which is $16times$ that of this magnet, then its periodic time will be ____.

• A. $T/2$
• B. $2T$
• C. $T/4$
• D. $4T$

Answer 1

The correct option is C $T/4$

$T=2\pi \sqrt{\frac{I}{MB}}$ where $M=$dipole moment.

$⟹T\alpha \frac{1}{\sqrt{m}}⟹T^{\prime }\alpha \frac{1}{\sqrt{16m}}⟹\frac{T^{\prime }}{T}=\frac{1}{4}$

$⟹T^{\prime }=\frac{T}{4}$