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Magnetism and Matter
Magnetic Moment of a Bent Bar Magnet
2 questions from 2 papers, each with its answer.
- questions
- 2
- papers
- 2
- years asked, 2017–2026
- 1 of 10
- of Magnetism and Matter
- 5.26%
Concepts tested
- Magnetic moment of a bent bar magnet
- Vector addition of magnetic moment on bending a bar magnet
All Questions
2024 1 question
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An iron bar of length $L$ has magnetic moment $M$. It is bent at the middle of its length such that the two arms make an angle $60^\circ$ with each other. The magnetic moment of this new magnet is:Initially, M = ml (m = pole strength, l = length). When the rod is bent at the middle, each arm is $\frac{l}{2}$ and the arms make $60^\circ$ with each other. [add image: bar bent at the middle into two arms of length l/2 at $60^\circ$] Effective length $l_{eff} = 2 \times \frac{l}{2}\sin 30^\circ = \frac{l}{2}$ $M' = m \times \frac{l}{2} = \frac{M}{2}$
2024 Re-NEET 1 question
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The magnetic moment of an iron bar is M. It is now bent in such a way that it forms an arc section of a circle subtending an angle of $60^\circ$ at the centre. The magnetic moment of this arc section isFrom $R\theta=L$ (arc length equals original bar length), $R=\dfrac{L}{\theta}=\dfrac{3L}{\pi}$ (for $\theta=\pi/3$). The new magnetic moment (effective dipole length is the chord $2R\sin30^\circ$): $M'=m(2R)\sin30^\circ=m\times2\times\dfrac{3L}{\pi}\times\dfrac{1}{2}=\dfrac{3mL}{\pi}=\dfrac{3M}{\pi}$.