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. `(2M)/(pi)`
C. `M//pi`
D. none of the above

Answer

B

Explanation

After beding , distance between poles = 2 r
Earlier distance ` = l (pi r)`
` (M)/(M) = (m xx 2r)/(m xx pir) = (2)/(pi)`
`therefore M . = M xx (2)/(pi)`