Question

If a bar magnet of pole strength $m$ and magnetic moment $M$ is cut perpendicular to its axis in two equal halves then its new pole strength $m^{\prime }$ and magnetic moment $M^{\prime }$ are respectively

• A. $m^{\prime }=m$ and $M^{\prime }=M$
• B. $m^{\prime }=m$ and $M^{\prime }=\frac{M}{2}$
• C. $m^{\prime }=\frac{m}{2}$ and $M^{\prime }=2M$
• D. $m^{\prime }=2m$ and $M^{\prime }=\frac{M}{2}$

Answer 1

Answer: (B)

When a bar magnet cut perpendicular to its axis into two equal parts then $m^{\prime }=m$ and length ${\ell }^{\prime }=\frac{\ell }{2}$
$\therefore M=m\ell =m\frac{\ell }{2}=\frac{M}{2}$