A magnetised wire of magnetic moment M and length L is bent in the form of a semicircle of radius r. The new magnetic moment is :

Options

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

Answer

D

Explanation

Length of semicircle `pir=l`
where `" "r=l/pi`
Distance between two poles in semicircle = 2r.
Magnetic moment `M=m times 2r=M/l times (2l)/pi=(2M)/pi`