The B-H curve or magnetization curve is the graph plotted between magnetic flux density (B) and magnetizing force (H = NI/l). The B-H curve indicates the manner in which the magnetic flux density varies with the change in magnetizing force.
Fig. 1: Complete B H Curve
Magnetic permeability is defined as the ratio of magnetic flux density B produced within a material by a magnetizing field and the magnetic field intensity H. It is a scalar quantity and denoted by the symbol μ. It is the slope of the B-H curve.
$$ \mu=\ \frac{B}{H} $$
Magnetic permeability helps us measure a material’s resistance to the magnetic field or measure of the degree to which magnetic field can penetrate through a material.
Types of Permeability
The different types of permeability include;
Permeability of Free Space ($\mu_0$)
Permeability of free space also known as the permeability of air or vacuum is represented by μ0=B0/H
Permeability of Medium
The ratio of magnetic intensity in the medium and magnetizing field. It is expressed as μ = B/H
Relative Permeability Relative permeability is a dimensionless quantity. It is the ratio of two quantities with the same units, so relative permeability has no unit. Relative permeability of free space is 1.
Its expression is given as - μr= μ/μ0
Relative permeability = (number of lines of magnetic induction per unit area in a material)/(number of lines per unit area in a vacuum)
Relative permeability of magnetic materials is in the range of 800 -1000.
The Remanent Magnetization or Retentivity or Residual Flux density (Br)