Question

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

• A. $ 2π\, Am^2 $
• B. $ \frac{1}{π}\, Am^2 $
• C. $ π\, Am^2 $
• D. $ \frac{2}{π}\, Am^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=2 \,m ] $
Magnetic moment $M=n I A$
$=1 \times 1 \times \pi\left[\frac{1}{\pi}\right]^{2} $
$=\frac{1}{\pi} \,Am ^{2}$