Question

The magnetic moment of an iron bar is M. It is now bent in such a way that it forms an arc section of a circle subtending an angle of 60° at the centre. The magnetic moment of this arc section is

• A. $\frac{3M}{\pi}$
• B. $\frac{4M}{\pi}$
• C. $\frac{M}{\pi}$
• D. $\frac{2M}{\pi}$

Answer 1

Answer: (A)

$\frac{3M}{\pi}$

Answer 2

R0 = L

$\frac{R\pi}{3}$ = L

R = $\frac{3L}{\pi}$

M' = m(2R) sin 30°

= m(2)$\frac{3L}{\pi}$ × $\frac{1}{2}$ = $\frac{3}{\pi}$mL = $\frac{3M}{\pi}$