The effective length of magnet is 31.4 cm and its pole strength is 0.8 Am. The magnetic moment, if it is bent in the form of a semicircle is ..... A-m². [Guj. CET 2015]

The effective length of magnet, l = 31.4 cm = 31.4 x 10^-2 m
Pole strength, m = 0.8 Am

Length of semi-circle  $=\pi \frac{D}{2}=l$

where, D = diameter of circle

$\Rightarrow D=\frac{2l}{\pi }=\frac{2\times 31.4\times {10}^{-2}}{3.14}$

$\Rightarrow D=20\times {10}^{-2} \mathrm{m}$

Now, the magnetic moment

$=mD=0.8\times 20\times {10}^{-2}$

$=16\times {10}^{-2}=0.16 \mathrm{A}-{\mathrm{m}}^2$