Question

A bar magnet of magnetic moment $3.0A-m^2$ is placed in a uniform magnetic induction field of $2\times {10}^{-5}T$. If each pole of the magnet experiences a force of $6\times {10}^{4}N$, the length of the magnet is

• A. 0.5 m
• B. 0.3 m
• C. 0.2 m
• D. 0.1 m

Answer 1

The correct option is D 0.1 m

$F=mB\Rightarrow F=\frac{M}{L}\times B$
$\Rightarrow 6\times {10}^{-4}=\frac{3}{L}\times 2\times {10}^{-5}\Rightarrow L=0.1m$