Magnetic Potential EnergyA magnetic dipole moment in a magnetic field will possess potential energy which depends upon its orientation with respect to the magnetic field. Since magnetic sources are inherently dipole sources which can be visualized as a current loop with current I and area A, the energy is usually expressed in terms of the magnetic dipole moment:
The energy is expressed as a scalar product, and implies that the energy is lowest when the magnetic moment is aligned with the magnetic field. The difference in energy between aligned and antialigned is
The expression for magnetic potential energy can be developed from the expression for the magnetic torque on a current loop. These relationships for a finite current loop extend to the magnetic dipoles of electron orbits and to the intrinsic magnetic moments associated with electron spin and nuclear spin. 
Index Magnetic field concepts Currents as magnetic sources  

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