Question

A long magnetic needle of length $2L$, magnetic moment $M$ and pole strength $m$ units is broken into two pieces at the middle along its length. The magnetic moment and pole strength of each piece will be

• A. $M,m$
• B. $\frac{M}{2},\frac{m}{2}$
• C. $M,\frac{m}{2}$
• D. $\frac{M}{2},m$

Answer 1

The correct option is D $\frac{M}{2},m$


$M=ml=2mL$
Pole strength of each part $=m$
Magnetic moment of each part
$=M^{\prime }=m^{\prime }{L}^{\prime }=mL=\frac{M}{2}$