If a steel wire of length l and magnetic moment M is bent into a semicircular are, the the new magnetic moment is

Options

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

Answer

C

Explanation

When wire is bent in the form of semicircular are the, `I=pir`
`therefore`The radius of semicircular are, `r=l/pi`
Distance between two end points of semicircular wire
Magnetic moment of semicircular wire
But ml is the magnetic straight wire i.e. ml=M
`therefore "New Magnetic moment" =(2)/(pi)M`