Two magnects of magnetic moments M and `Msqrt3` are joined to form a cross (+). The combination is suspended freely in a uniform magnetic field. In equilibrium position, the magnet of magnetic moment M makes an angle `theta` with the field. Determine `theta`.

Answer

`60^@`

Explanation

When magnet of magnetic moment `M_1=M` makes `/_theta` with the field, the other magnet of mangetic moment `M_2=Msqrt3` will make an angle `(90^@-theta)` with the field. In equilibrium,
`tau_1=tau_2`
`M_1Bsintheta=M_2Bsin(90^@-theta)`
`MBsintheta=Msqrt3Bcostheta`,
`(sin theta)/(costheta)=sqrt3`,
i.e. `tan theta = sqrt3`, `:. theta=60^@`