Question

A bar magnet of magnetic moment 3.0 Amp ×m 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. 0.1m

Answer 1

Answer: (D)

0.1m

Answer 2

$M = m L$ and $F = m B$ ,⇒ $F = \frac { M } { L } \times B$ ⇒

$6 \times 10 ^ { - 4 } = \frac { 3 } { L } \times 2 \times 10 ^ { - 5 } \Rightarrow L = 0.1 \mathrm {~m}$