**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.

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 + B_{m}

Where,

B_{m} = The field contributed by the core material. Here,

B_{m} α Magnetization of the material (M).

Mathematically,

B_{m} = 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 = µ₀µ_{r}H = µH

Here,

µ_{r} = 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 = µ₀µ_{r} = µ₀ (1 + χ).