Magnetization and Magnetic Intensity

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 and Magnetic Intensity

Magnetization: Magnetization of a given sample material M, can be defined as the net magnetic moment for that material per unit volume.

Mathematically,

\(M\,=\,\frac{{{m}_{net}}}{V}\),

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

Where,

Bm = The field contributed by the core material. Here,

Bm α Magnetization of the material (M).

Mathematically,

Bm = µ₀M

Here,

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,

\(H\,=\,\frac{B}{{{\mu }_{0}}}\,-\,M\),

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

Where,

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

Here,

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).