Eddy Currents: Circulating electrical currents that areinduced in electrically conductive elements when exposed to changing magnetic fields, creating an opposing force to the magnetic flux. Eddy currents can be harnessed to perform useful work (such as damping of movement) , or may be unwanted consequences of certain designs which should be accounted for or minimized.

Ferromagnetic Material: A material whose pemeability is very much larger than 1 (from 60 to several thousand times 1),and which exhibits hysteresis phenomena.

Flux, O :The condition existing in a medium subjected to a magnetizing force. This quantity is characterized by the fact that an electromotive force is induced in a conductor surrounding the flux at any time the flux changes in magnitude. The cgs unit of flux is the maxwell .

Fringing Fields: Leakage flux particularly associated with edge effects in a magnetic circuit.

Gauss: Lines of magnetic flux per square centimeter, cgs unit of flux density, equivalent to lines per square inch in the English system, and webers per square meter or Tesla in the SI system.

Hysteresis Loop: A closed curve obtained for a material by plotting corresponding values of magnetic induction , B , (on the abscissa) against magnetizing force, H (on the ordinate).

Induction, B: The magnetic flux per unit area of a section normal to the direction of flux. Measured in Gauss, in the cgs system of units.

Intrinsic Coercive force, Hci: Measured in Oersteds in the cgs system, this is a measure of the material's inherent ability to resist demagnetization. It is the demagnetization force correponding to zero intrinsic induction in the magnetic material after saturation. Practical consequences of high Hci values are seen in greater temperature stability for a given class of material, and greater stability in
dynamic operating conditions.

Irreversible Loss: Defined as the partial demagnetization of a magnet caused by external fields of other factors. These losses are only recoverable by remagnetization . Magnets can be stabilized to prevent the variation of performance caused by irreversible losses.