Spread the love

Intensity of Magnetisation

Intensity of Magnetisation :- When a substance is placed in an external magnetic field, the atomic dipoles of the substance become partially or completely aligned. When this happens, a net magnetic moment is developed in every microscopic volume of the substance, hence

The value of the total magnetic moment produced per unit volume of a substance is called the intensity of magnetisation of that substance.

M = magnetic moment produced in matter

V = volume of substance

Then intensity of magnetisation (magnetization intensity) :-

$\displaystyle \overrightarrow{I}=\frac{\overrightarrow{M}}{V}$ …..(1)

A = cross sectional area of material

l = effective magnetic length of material

m = pole strength

Then equation (1) can be written as :-

$\displaystyle I=\frac{m\times l}{A\times l}=\frac{m}{A}$ …..(2)

Hence

The value of pole strength per unit area of a substance is called the intensity of magnetisation of that substance.

Intensity of magnetisation is a vector quantity and its direction is from the south pole to the north pole in the material.

The value of Intensity of magnetisation depends on the nature of the material and its temperature.

Unit of Intensity of Magnetisation

$\displaystyle I=\frac{M}{V}=\frac{A\times {{m}^{2}}}{{{m}^{3}}}=A{{m}^{-1}}$

$\displaystyle I=\frac{m}{A}=\frac{A-m}{{{m}^{2}}}=A{{m}^{-1}}$

Hence unit of intensity of magnetisation is $\displaystyle A{{m}^{-1}}$

Example 1.

The magnetic moment of a bar magnet of mass 75 grams is 9 × 10⁻⁷ A-m². If the density of the material of the magnet is 7.5 × 10³ then the intensity of magnetisation will be :-

$(A) 90 Am-1$

(B) 0.09 $Am-1$

$(C) 9 Am-1$

(D) 0. $9 Am-1$

Solution:

Intensity of magnetisation,

$\displaystyle I=\frac{M}{V}$

$\displaystyle \Rightarrow I=\frac{M}{{}^{m}\!\!\diagup\!\!{}_{\rho }\;}$

$\displaystyle I=\frac{M\rho }{m}=\frac{9\times {{10}^{-7}}\times 4.5\times {{10}^{3}}}{75\times {{10}^{-3}}}$

$\displaystyle I=0.09A{{m}^{-1}}$

Intensity of Magnetisation

Unit of Intensity of Magnetisation

Like this: