A current loop in a magnetic field

Options

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

Answer

B

Explanation

When a current loop is placed in magnetic field it experieces a torque. It is given by
`vec tau = vec M xx bec B`
where `vec M ` is the magnetic moment of the loop and `vec B ` si teh magnetic field .
or `tau = MB` sin `theta` Where `theta ` are parallel (i.e `theta= 0^@)` the equilibrium is stable and when they are antiparallel (i.e `theta = pi)` the equlibrium is unstable.