A current loop in a magnetic field

Options

A. Can be in equilibrium in two orientations, one stable while the other is unstable
B. Experiences a torque whether the field is uniform or non uniform in all orientations
C. Can be in equilibrium in one orientation
D. Can be in equilibrium in two orientations, both the equilibrium states are unstable

Answer

A

Explanation

`vectau = vecm xx vecB = mB sin theta`
`U = -vecm.vecB = -mB cos theta`
When `theta = 0^(@) , tau = 0` and `U_("min") = -mB to` stable equilibrium
When `theta = 180^(@) , tau = 0` and `U_("max") = mB to ` unstable equilibrium