Question

If a bar magnet of pole strength $m$ and magnetic moment $M$ is cut equally $4$ times parallel to its axis and $3$ times perpendicular to its axis then the pole strength and magnetic moment of each piece are respectively

• A. $\frac{m}{20},\frac{M}{20}$
• B. $\frac{m}{4},\frac{M}{20}$
• C. $\frac{m}{5},\frac{M}{20}$
• D. $\frac{m}{5},\frac{M}{4}$

Answer 1

Answer: (C)

Pole strength $m$ is directly proportional to cross-sectional area.
$m^{\prime }=\frac{m}{5}{M}^{\prime }=\frac{M}{5\times 4}$