Magnetization and Magnetic Intensity
The Magnetic behaviour of a magnet is characterized by the alignment of the atoms inside a substance. When a ferromagnetic substance is brought under the application of a strong external magnetic field, then they experience a torque wherein the substance aligns themselves in the direction of the magnetic field applied and hence gets strongly magnetized in the direction of the magnetic field.
Magnetization: Magnetization of a given sample material M, can be defined as the net magnetic moment for that material per unit volume.
Let us now consider the case of a solenoid. Let us take a solenoid with n turns per unit length and the current passing through it be given by I, then the magnetic field in the interior of the solenoid can be given as, B₀ = µ₀nI
Now, if we fill the interior of the solenoid with a material of non-zero magnetization, the field inside the solenoid must be greater than before. The net magnetic field B inside the solenoid can be given as,
B = B₀ + Bm
Bm = The field contributed by the core material. Here,
Bm α Magnetization of the material (M).
Bm = µ₀M
µ₀ = Constant of permeability of vacuum.
Let us now discuss another concept here, the magnetic intensity of a material. The magnetic intensity of a material can be given as,
From this equation, we see that, the total magnetic field can also be defined as,
B = µ₀ (H + M)
Here, the magnetic field due to the external factors such as the current in the solenoid is given as H and that due to the nature of the core is given by M. The latter quantity, that is M is dependent on external influences, and is given by, M = χH
χ = Magnetic susceptibility of the material.
It gives the measure of the response of a material to an external field. The magnetic susceptibility of a material is small and positive for paramagnetic materials and is small and negative for diamagnetic materials.
B = µ₀ (1 + χ) H = µ₀µrH = µH
µr = Relative magnetic permeability of a material.
Which is analogous to the dielectric constants in the case of electrostatics. We define the magnetic permeability as, µ = µ₀µr = µ₀ (1 + χ).