If the magnetic moment of a straight magnetised wire is `p_(m)` , what will be its magnetic moment when the wire is bent in the form of a semicircle ?

Explanation

Let the length of the magnetised wire be l .
`therefore` pole-strength of the wire , `m=(p_(m))/(l)`
When the wire is bent in the form of semicircle , its effective length = diameter of the semicircle = 2r .
According to the problem , `pir=l" or, "r=(l)/(pi)`
`therefore` The changed magnetic moment of the wire
= effective length `xx` pole - strength
`2rxx(p_(m))/(l)=(2l)/(pi).(p_(m))/(l)=(2p_(m))/(pi)`