Magnetic energy and electric energy are related by Maxwell's equations. The potential energy of a magnet of magnetic moment, m, in a magnetic field, B, is defined as the mechanical work of magnetic force (actually of magnetic torque) on re-alignment of the vector of the Magnetic dipole moment, and is equal:
This second expression forms the basis for superconducting magnetic energy storage.
Energy is also stored in a magnetic field. The energy per unit volume in a region of space of permeability, μ, containing magnetic field, B, is:
More generally, if we assume that the medium is paramagnetic or diamagnetic so that a linear constitutive equation exists that relates B and H, then it can be shown that the magnetic field stores an energy of
where the integral is evaluated over the whole region where the magnetic field exists.
- Magnetic Energy, Richard Fitzpatrick Professor of Physics The University of Texas at Austin.
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