Question

The effective length of a magnet is $31.4cm$ and its pole strength is $0.8Am$. The magnetic moment, if it is bent in the form of a semicircle is _____ $A{m}^2$.

• A. $1.2$
• B. $1.6$
• C. $0.16$
• D. $0.12$

Answer 1

The correct option is C $0.16$

The effective length of magnet $=31.4cm$
Pole strength $m=0.8Am$
Length of semi-circle $=\pi \frac{D}{2}=l$
where, $D=$ diameter of circle
$\Rightarrow D=\frac{2l}{m}$
$=\frac{2\times 314\times {10}^{-2}}{3.14}$
$D=20\times {10}^{-2}m$
Now, the magnetic moment
$=ml=mD$
$=0.8\times 20\times {10}^{-2}$
$=16.0\times {10}^{-2}=0.16A{m}^2$.