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NTA Abhyas 2020
Exam
NTA Abhyas
Year
2020
Subject
Physics
Chapter
Magnetic Properties of Matter

NTA Abhyas 2020 · Physics · Magnetic Properties of Matter

A long thin magnet of magnetic moment M is bent into a semi-circle....

A long thin magnet of magnetic moment MM is bent into a semi-circle. The decrease in the magnetic moment is

Options

  1. A2Mπ\dfrac{2M}{\pi}
  2. B\piM2\dfrac{\piM}{2}
  3. C\dfrac{M\left(\pi - 2\right)}{\pi}
  4. D\dfrac{M\left(2 - \pi\right)}{2}

Correct answer

C. \dfrac{M\left(\pi - 2\right)}{\pi}

Step-by-step solution

Magnetic length is the minimum distance between the north pole and the south pole, which is decreased in the second case.

M′=2MπM^{′} = \dfrac{2M}{\pi}, decrease in magnetic moment

=M−2Mπ= M - \dfrac{2M}{\pi}
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