A magnetic dipole is acted upon by two magnetic fields with inclined to each other at an angle of `75^(@)`. One of the fields has a magnitude of 15 mT. The dipole attains stable equilibrium at an angle of `30^(@)` with this field. The magnitude of the other field (in mT) is close to

Options

A. 1
B. 11
C. 36
D. 1060

Answer

b

Explanation

(b) We know that, magnetic dipole moment
`M=NiA cos theta i.e., M prop cos theta`
When two magnetic fields are inclined at an angle of `75^(@)` the equilibrium will be at `30^(@)`, so
`cos theta=cos (75^(@)-30^(@))=cos 45^(@)=(1)/(sqrt2)`
`(x)/(sqrt2)=(15)/(2) therefore x ~~11`