Q 12-05-007NEETJEE MainEAMCET 2007 (Engineering)Medium
A bar magnet has moment of inertia $49 \times 10^{-2}\ \text{kg m}^2$ and vibrates in a magnetic field of induction $0.5 \times 10^{-4}$ T. The time period of vibration is $8.8$ s. The magnetic moment of the bar magnet is
Answer: (D) $500\ \text{A m}^2$
$T = 2\pi\sqrt{\dfrac{I}{MB}} \Rightarrow M = \dfrac{4\pi^2I}{T^2B} = \dfrac{39.5 \times 0.49}{77.44 \times 0.5 \times 10^{-4}} \approx 500\ \text{A m}^2$.
Solution by Sreeraj P, M.Sc Physics