Chapter-4|Moving Charges and Magnetism| NCERT 12th Physics:
Torque On a Current Loop In a Uniform Magnetic Field (Magnetic Dipole):
Let we consider a rectangular loop ABCD be suspended in a uniform magnetic field B. Let AB=CD=b and AD=BC=a and I be the current flowing through the loop.
Case-1:The rectangular loop is placed such that the uniform magnetic field B is in the same plane of the loop.
Case-2: The plane of the loop is not along the magnetic field, but makes an angle θ with it.
Note: If we rotate loop θ with magnetic field, then the angle between magnetic moment and magnetic field also will be θ, because M is always perpendicular to A( Area enclosed by the loop).