A current carrying circular loop of radius R is placed in the x-y plane with centre at the origin. Half of the loop with `xgt0` is now bent so that it now lies in the y-z plane.

Options

A. The magnitude of magnetic moment now diminishes
B. The magnetic moment does not change
C. The magnitude of B at (0, 0 , z) z `gt R` increase
D. The magnitude of B at (0,0, z) `z gt gt R` is unchanged

Answer

A

Explanation

The direction of magnetic moment of circular loop of radius R placed in the x-y plane is along z-direction and given by `M = I (pi r^2)` when half of the loop with `0 gt x` is now bent so that it now lies in the y-z plane, the magnitudes of magnetic moment of each semicircular loop of radius R lie in the x-y plane and the y-z plane is `M. = l (pi r^(2) //4)` and the direction of magnetic moments are along z–direction and  x direction respectively. Their resultant
`M_("net") = sqrt(M^(2+) + M^(2)) = sqrt2 M = sqrt2 I (pi r^2) //4`
So , `M_("net") lt M` or M diminishes.