Page 476 - Basic Electrical Engineering

density B, when a magnetic material is magnetized by applyingMMF. If we
plot the flux density, B against the magnetizing force applied, H, we will get
a linear relationship as shown so in Fig. 5.5 so that

B α H

or,

B = K H

This constant K is called the permeability of the core material and is
denoted by μ. Thus, we can write

B = μH (5.4)

Since this equation is similar to the equation of a straight line passing
through the origin (y = mx), the slope will depend on the value of

permeability, μ. Permeability is the magnetic property of the core material.
The core may be, e.g. air, cardboard, bakelite former, or iron.

5.1.4 Permeability

Permeability is the measure of how well the material conducts magnetism or
allows the establishment of magnetic field through it. As shown in Fig. 5.5
(b), material 2 is more permeable than material 1.

The graphic representation of the relationship between B and H is called
the magnetization curve. In the case of air core coil, the magnetization curve

is a straight line with a small slope with the H-axis showing that a large value
of H is required to produce a small amount of flux or flux density. If iron is

used as the core material the slope will greatly increase indicating that a small
magnetizing force produces a large amount of flux and a high value of flux

density.