NEETPhysicsMagnetism and MatterMCQ+4 / −1
The magnetic moment of an iron bar is . It is now bent in such a way that it forms an arc section of a circle subtending an angle of at the centre. The magnetic moment of this arc section is
- A
- B
- C
- D
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Correct answer: A
$M=m \cdot L$
$$\begin{aligned} \& R \theta=L \\ \& \frac{R \pi}{3}=L \\ \& R=\frac{3 L}{\pi} \\ \& M^{\prime}=m(2 R) \sin 30^{\circ} \\ \& =m(2) \frac{3 L}{\pi} \times \frac{1}{2}=\frac{3}{\pi} m L=\frac{3 M}{\pi} \end{aligned}$$
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