question_answer

A long magnetic needle of length 2L, magnetic moment M and pole strength m units is broken into two pieces at the middle. The magnetic moment and pole strength of each piece will be                  [NCERT 1983; DPMT 1987]

A)            \[\frac{M}{2},\frac{m}{2}\]   

B)            \[M,\frac{m}{2}\]

C)            \[\frac{M}{2},m\]              

D)            \[M,m\]

Correct Answer: C

Solution :

                   Pole strength of each part =m Magnetic moment of each part \[={M}'={m}'{L}'=mL=\frac{M}{2}\]