A magnet with moment M is given. If it is bent into a semicircular form, its new magnetic moment will be:

Options

A. M
B. 2M
C. `2M//pi`
D. `M//2pi`

Answer

C

Explanation

`Radius=r,therefore l=pi r therefore r=(1)/(pi)`
Distance between two poles`=2 r=(2l)/(pi)`
pole strength `m=(M)/(l)`
Thus magnetic moment`=(M)/(l)(2l)/(pi)=(2M)/(pi)`