Magnetic permeability represents the ease with which a material allows magnetic force of lines to pass through it. The permeability of vacuum or free space is denoted by μ0 and it is taken as the standard with respect to this the permeability of all materials is expressed. The permeability of the medium of a material is denoted as μ; it is the product of the permeability of free space (μ0) and relative permeability (μr).
∴ μ = μrμ0 H/M
μr is purely a number; it has no units. The permeability of free space is:
μ0 = 4π × 10−7 H/M
Let B be the magnetic flux density in a magnetic material by applying magnetic field of intensity H and B0 be the flux density at the same place if the material is removed [i.e., in air or vacuum]. ...