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Question: Answered & Verified by Expert
A steel wire of length $\ell$ has a magnetic moment M. It is then bent into a semicircular arc. The new magnetic moment is
PhysicsMagnetic Effects of CurrentVITEEEVITEEE 2018
Options:
  • A $\frac{\mathrm{M}}{\pi}$
  • B $\frac{2 \mathrm{M}}{\pi}$
  • C $\frac{3 \mathrm{M}}{\pi}$
  • D $\frac{4 M}{\pi}$
Solution:
1411 Upvotes Verified Answer
The correct answer is: $\frac{2 \mathrm{M}}{\pi}$
Let pole strength $=\mathrm{m}$
So, $\mathrm{M}=\mathrm{m} \ell$
When wire is in form of arc, then the distance between poles $=\frac{2 \ell}{\pi}$
So, $M^{\prime}=\frac{m 2 \ell}{\pi}=\frac{2 M}{\pi}$

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