12.3.A.1 Magnetic permeability is a measurement of the amount of magnetization in a material in response to an external magnetic field.
12.3.A.2 Free space has a constant value of magnetic permeability that appears in physical relationships.
12.3.A.3 The permeability of matter has a value different from that of free space that arises from the matter’s composition and arrangement. It is not a constant for a material and varies based on many factors including temperature, orientation, and strength of the external field.