Reluctance, R: Analogous to resistance in an electrical circuit, reluctance is related to the magnetomotive force, F, and the magnetic flux, Ø by the equation R = F/Ø, (paralleling Ohm’s Law) where F is the magnetomotive force, and Ø is the magnetic flux, (in cgs units).

Permeance Coefficient, Pc: Raio of the magnetic induction, Bd, to its self demagnetizing force , Hd. Pc =  Bd/Hd. This is also known as the “load line” or operating point of the magnet, and is useful in estimating the flux output of the magnet in various conditions. As a first order approximation, Bd/Hd = Lm/Lg, where Lm is the length of the magnet, and Lg is the length of an air gap that he magnet is subjected to. Pc is therefore a function of the geometry of the magnetic circuit.

Relative Permeability, µ_r: The ratio of permeability of a medium to that of a vacuum; µ_r = µ/ µ₀. In the cgs system, µ₀ = 1 in a vacuum by definition,. The permeability of air is also for all practical purposes equal to 1 in the cgs system.

Permeance: The inverse of reluctance, analogous to coductance in electrical circuits.

Pole pieces: Ferromagnetic materials placed on magnetic pole used to shape and alter the effect of lines of flux.

Paramagnetic Material: A material having a permeability slightly greater than 1.