Engineering Physics

7.1 Magnetic permeability

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 (μ_r).

∴ μ = μ_rμ₀ H/M

μ_r 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]. ...