Question

A bar magnet has been cut equally lengthwise and width wise to give four equal pieces. What is pole strength of each piece as compared to the pole strength of original bar magnet ?

• A. Same
• B. $\frac{1}{8}$
• C. $\frac{1}{4}$
• D. $\frac{1}{2}$

Answer 1

The correct option is C $\frac{1}{4}$

$M=m\times l$

when magnet is cut into 4 parts its m as well as l changes

$m^{\prime }=\frac{m}{2},l^{\prime }=\frac{l}{2}$

$\therefore M^{\prime }=m^{\prime }\times l^{\prime }=\frac{ml}{4}=\frac{M}{4}$