Question

A wire of length $2m$ carrying a current of $1A$ is bent to form a circle, the magnetic moment of the coil is

• A. $2\pi A{m}^2$
• B. $\frac{1}{\pi }A{m}^2$
• C. $\pi A{m}^2$
• D. $\frac{2}{\pi }A{m}^2$

Answer 1

Answer: (B)

Circumference $=$ length of the wire
$2\pi r=L$
$r=\frac{L}{2\pi }$
$r=\frac{1}{\pi }[\because L=2m]$
Magnetic moment $M=nIA$
$=1\times 1\times \pi {\left[\frac{1}{\pi }\right]}^2$
$=\frac{1}{\pi }A{m}^2$