A current carrying circular loop of radius R is placed on the xy place with centre at the origin . Half of the loop with `xgt0` is now bent so that it now lies on the yz plane .

Options

A. the magnitude of magnetic moment now diminishes
B. the magnetic moment does not change
C. the magnitude of `vec(B) " at " (0 , 0, z), (zgtgtR)` increases
D. `vec(B) " at " (0 , 0, z), (zgtgtR)` is unchanged

Answer

A

Explanation

when the circular loop is placed in xy plane , then
`M=IxxpiR^(2),` along + ve z - axis
When half of the loop is bent on yz plane , the magnetic moment of this portion of the loop ,
`M_(1)=(I.piR^(2))/(2)` , along positive x - axis
The magnetic moment of the other portion of the loop (in xy plane )
`M_(2)=(IpiR^(2))/(2)` , along positive z - axis
`therefore` Resultant moment ,
`M'=sqrt(M_(1)^(2)+M_(2)^(2))=(sqrt(2))/(2).IpiR^(2)ltM`