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:

  1. (a) Magnetic dipole moment

$M=m \times \ell \quad M^{\prime}=m \times r$

From figure

$\ell=\frac{\pi r}{3} \quad$ or $\quad r=\frac{3 \ell}{\pi}$