# Magnetisation and Magnetic Intensity

## Introduction to Magnetisation 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.

## Magnetic Intensity or Intensity of Magnetic Field

The magnetic intensity at a point is defined as the force that unit north - Pole experiences when it is placed in that field.

The intensity of magnetic field at P due to single pole is given by:

Fig: Intensity of magnetic field at P due to single north pole

## Intensity of Magnetic field due to a magnet at different points

### In Longitudinal Position

+/-m = Magnitude of south and north poles

r = Distance of point P from the centre of the magnet

l = Length of the bar magnet

∴ Intensity of magnetic field at pointP is given by,

Where M is the magnetic  moment = 2*m*l

Case a: For a small magnet,

r≫ l2

### In Transverse Position

Intensity of magnetic field at point P is given by,

When the magnet is of short length,

### In Any General Position

The direction of is always parallel to the axis from the north to south pole in magnet.

## Meaning or Definition of Intensity of Magnetisation

The Magnetic moment of a magnet undergoes a change when it is placed in a magnetic field. This change that is, the magnetic moment change per unit volume is known as in Intensity of Magnetisation.

## Formula of Intensity of Magnetisation

Where, m – Pole strength

A  -  Area of cross section

## Intensity of Magnetisation Unit

The S.I unit of intensity of magnetisation is Ampere/metre or A/m

## Difference between Magnetic Intensity and Intensity of Magnetisation

The magnetic intensity defines the forces that the poles of a magnet experiences in a magnetic field whereas the intensity of magnetisation explains the change in the magnetic moment of a magnet per unit volume.

Q1. What is H in magnetism?

Sol. H in magnetism is defined as the magnetic field strength that is, the strength of the field that a magnet has to attract or repel other substance.

Q2. What is the magnetic field intensity?

Sol. The magnetic field intensity at any point is defined as the force experienced by the point when placed under the influence of an external magnetic field.

Q3. What is meant by magnetisation?

Sol. Magnetisation can be defined as a process in which a substance is made a permanent or temporary magnet by exposing them to an external magnetic field.

Q4. What is induced magnetisation?

Sol. Induced magnetisation can be defined as the process in which a non-magnetic material can be magnetized by bringing it under the influence of an external magnetic field.

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Magnetisation and Magnetic Intensity

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