Two bar magnet with magnetic moment `2M` and `M` are fastened togather at right angles to each other at their centres to from a cross system, which can rotate freely about a vertical axis through the centre. The crossed system sets in earth's magnetic field with magnet having magnetic moment `2M` making and angle `theta` with the magnetic merdian such that

Options

A. `theta=tan^(-1)(1/sqrt(3))`
B. `theta=tan^(-1)(sqrt(3))`
C. `theta=tan^(-1)(1/2)`
D. `theta=tan^(-1)(3/4)`

Answer

C

Explanation

`implies tantheta=M/(2M)=1/2 implies theta = tan^(-1)=1/2`