Also called the load-line, B/H or "operating slope" of a magnet, this is the line on the Demagnetization Curve where a given magnet operates. The value depends on both the shape of the magnet, and it's surrounding environment (some would say, how it's used in a circuit). In practical terms, it's a number that define how hard it is for the field lines to go from the north pole to the south pole of a magnet. A tall cylindrical magnet will have a high Pc, while a short, thin disc will have a low Pc. Permeance Coefficient has the symbol (P_c).