The torque on a current loop is given by:

t = IA ´ B

We can define something called the magnetic dipole moment, m:

For a single loop, m = IA

For a coil with N turns, m = NIA

The torque is then given by:

t = m ´ B

A loop, or coil, in a uniform magnetic field has a potential energy given by:

U = -m · B