Question

A bar magnet of magnetic moment $3.0\, A \,m ^{2}$ 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

Answer: (D)

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