A steel wire of length L has a magnetic moment M. It is then bent into a semi-circular arc; the new magnetic moment will be :
Options

Question

A steel wire of length L has a magnetic moment M. It is then bent into a semi-circular arc; the new magnetic moment will be :

G1 Physics · Accepted Answer

Magnetic moment=pole strength×magnetic length. Bending the wire into a semicircle keeps pole strength unchanged, while end separation becomes the diameter 2L/π. Thus M'=M(2/π). Hence B.