A bar magnet of magnetic moment M is bent into a semicircle. What is its new magnet moment ?

Explanation

Initial magnetic moment , M =2l m
Where .2l. is the length of the magnet and .m is the pole strength .
when the magnet is bent in the form of a semicircle of radius .r. the distance between the poles =2r
But the length of the magnet , `2l= pi r `
`implies r= (2l)/(pi)`
`:.` Length of the new magnet = Distance between the poles `=2.(2l)/(pi) `
New magnetic moment `, M^(1) = 2 xx (2l)/(pi) xx m = (2M)/(pi)` .