Magnetism and Matter - Result Question 2
2. A bar magnet of length ’ $\ell$ ’ and magnetic dipole moment ’ $M$ ’ is bent in the form of an arc as shown in figure. The new magnetic dipole moment will be
[2013]
(a) $\frac{3}{\pi} M$
(b) $\frac{2}{\pi} M$
(c) $\frac{M}{2}$
(d) $M$
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Answer:
Correct Answer: 2. (a)
Solution:
- (a) Magnetic dipole moment
$M=m \times \ell \quad M^{\prime}=m \times r$
From figure
$\ell=\frac{\pi r}{3} \quad$ or $\quad r=\frac{3 \ell}{\pi}$
