Q. 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 $m$
Explanation
(d) $F = mB \Rightarrow F = \frac{M}{L} \times B$
$\Rightarrow {6 \times 10}^{- 4} = \frac{3}{L} \times 2 \times 10^{- 5} \Rightarrow L = 0.1\ m$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.