Chapter: Magnetic Materials· Physics

A bar magnet of moment of inertia of 500 gcm2 oscillates with a time period of 3.142 seconds in a horizontal plane. What is its magnetic moment if the horizontal component of earth’s magnetic field is 4 × 10–5 T ?

Q.13 A bar magnet of moment of inertia of 500 gcm² oscillates with a time period of 3.142 seconds in a horizontal plane. What is its magnetic moment if the horizontal component of earth’s magnetic field is 4 × 10^–5 T ?

Doubtly Asked 29 Oct 2026 Board exam · July 2024 hsc 12th Save WhatsApp Report

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Answer: \(m = 5\) A m\(^2\)

Given \(I = 500\) g cm\(^2\) \(= 500\times10^{-3}\times10^{-4} = 5\times10^{-5}\) kg m\(^2\), \(T = 3.142\) s \(= \pi\) s, \(B_H = 4\times10^{-5}\) T.

\[T = 2\pi\sqrt{\frac{I}{mB_H}} \Rightarrow m = \frac{4\pi^2 I}{T^2 B_H}\]

Since \(T = \pi\), \(T^2 = \pi^2\):

\[m = \frac{4I}{B_H} = \frac{4\times5\times10^{-5}}{4\times10^{-5}} = 5\ \mathrm{A\,m^2}\]

Doubtly AI · 29 Oct 2026 AI-generated · not yet verified Report

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A bar magnet of moment of inertia of 500 gcm2 oscillates with a time period of 3.142 seconds in a horizontal plane. What is its magnetic moment if the horizontal component of earth’s magnetic field is 4 × 10–5 T ?

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