A straight wire carrying a current is turned into a circular loop if the magnitude of magnetic moment associated with it is M then the length of the wire will be

Options

A. `sqrt((4pi M)/(I))`
B. `sqrt((2pi M)/(I))`
C. `sqrt((piM)/(I))`
D. `sqrt((piM)/(2I))`

Answer

A

Explanation

M = IA = `I. pi r^(2)`
`implies r = sqrt((M)/(l pi))`
As l = `2pi r`
`implies l = 2pi sqrt((M)/(lpi)) = sqrt((4pi M)/(l))`