Question

A bar magnet of magnetic moment $M$ is cut into parts of equal lengths. The magnetic moment and pole strength of either part is

• A. $M/2,m/2$
• B. $M,m/2$
• C. $M/2,m$
• D. $M,m$

Answer 1

The correct option is C $M/2,m$

Given: Magnetic moment=M

Solution: Let pole strength =m

A dipole has a length of 2l initially then it is cut into two parts i.e.l and l

Before cut,

Magnetic moment=pole strength$\times 2l$

$M=m\times 2l$...........(1)

After cut,

Magnetic moment=pole strength$\times l$ (for each part)

$M^{{}^{\prime }}=m\times l$ (for each part) ..........(2)

combining eq. (1) &(2)

$M^{{}^{\prime }}=\frac{M}{2}$

But the pole strength remains same because dipole is cut vertically ,not horizontally

So,$m^{{}^{\prime }}=m$

Hence,the correct option is C