Question

Define Magnetization. State it’s formula and S I unit.

Answer 1

Hint: Magnetization gives an idea of whether a material can be magnetized or not. It is formed in a material due to induced magnetization by an external magnetic field. It can be defined as the ratio of magnetic moment to the total volume of the material.

Complete step by step answer:

So, in a material there can be magnetic dipoles present or a group of dipoles will be present. So when an external magnetic field is applied on the material, these dipoles or groups may align with the external magnetic field.

So, the magnetization of a material can be defined as the net magnetic moment per unit volume of the material. We can write it mathematically as

$\overrightarrow{M}={\displaystyle \frac{\overrightarrow{m_{net}}}{V}}$

$m_{net}$ is the net magnetic moment that is present in a material when an external field is applied.

V is the volume of the material.

The SI unit of magnetization is

 $\text{Ampere(metre}{\text{)}}^{-1}\text{ ,}\left({\displaystyle \frac{A}{m}}\right)$.

So when a material is magnetized, its own magnetic field will increase the total field that is present in the system.

The magnetic field that the material produces is directly proportional to the magnetization of the material. It is given by

$B_m={\mu }_{0}M$
Where,
$B_m$ is the magnetic field produced by the material.
${\mu }_0$ is the permeability of the material in a vacuum.

Note: The SI unit of magnetic moment is

$\text{Ampere(metre}{\text{)}}^2,\left(A{m}^2\right)$ and for volume is $metr{e}^3$.

Some materials like the ferromagnetic and ferromagnetic materials can retain their magnetic field even if the external magnetic field is switched off. This property is called retentivity. So, permanent magnets have high retentivity.

Coercivity is defined as the minimum value of magnetising intensity that is required to bring the material to its original state.
So an electromagnet which is always magnetized and demagnetized at regular intervals of time should have a high coercivity and low retentivity.