## Diamagnetic materials

Diamagnetic materials are those in which the individual atoms or molecules or ions do not possess any net magnet moment of their own.

When a sample of a diamagnetic material is placed in an external magnetic field of induction (B), a small magnetic moment is produced in each atom or molecule or ion proportional to B, but pointing in the opposite direction.

In other words, those materials which when placed in a magnetic field become weakly magnetized in a direction opposite to that of the applied field, are called as diamagnetic materials.

Example: bismuth, antimony, copper, gold, quartz, mercury etc.

## Relative magnetic permeability

Relative magnetic permeability is defined as the ratio of permeability of medium (μ) to the permeability of free space (μ0)

μr = μ/μ0

or                                 μr = B/H/(B0/H)

or                                 μr = B / B0

is permeability of free space.

## Magnetic permeability

Magnetic permeability is defined as the degree to which the magnetic lines of force can penetrate or permeate the material. It can also be defined as the ability of the material to permit the passage of magnetic lines of force through it.

As the magnetic induction is proportional to the magnetising field

B proportional H

or                     B = μH

where μ is called the permeability of the medium (material)

## Intensity of magnetisation

It represents the extent to which a specimen is magnetised when placed in a magnetising field.

Or in other words the  intensity of magnetisation of a magnetic material is defined as the magnetic moment per unit volume of the material.

M = Magnetic moment/volume = μM / V                            …1

Let       a = Uniform area of cross-section of the magnetised specimen.

l = magnetic length of the specimen.

m = strength of each pole of the specimen,

As                    μm = ml

and                   V = al

then equation (1) becomes

M = m x 2l / a x 2l

or         M = m/a

thus intensity of magnetisation of  a  magnetic material is also defined as the pole strength per unit area of cross-section of the material.

Unit :    M= magnetic moment / Volume

M= Amp.metre2 / metre3 = Am -1

These are S.I unit of M

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## Magnetic Intensity

Magnetic intensity is same as magnetizing force.

Therefore, it is also defined as the degree to which a magnetic field can magnetise a material is expressed in terms of magnetizing force.

Consider a toroidal solenoid with n turns per unit length carrying a current I. The magnetic induction of the field produced will be Continue reading “Magnetic Intensity”

## Magnetising Force

The degree to which a magnetic field can magnetise a material is expressed in terms of magnetizing force.

Consider a toroidal solenoid with n turns per unit length carrying a current I. The magnetic induction of the field produced will be Continue reading “Magnetising Force”

## Atomic Theory of Magnetism

The atomic theory of magnetism was given by Weber and modified by Ewing. According to this theory:

## Properties of magnets

Following are the some of the basic properties of magnets:

## Reason of magnetic effect in magnetic materials

The magnetic effects in a magnetic material are due to the atomic dipoles in the materials. These dipoles arise due to the tiny current loops of electrons in atomic orbits. Each revolving electron in the atomic orbit is equivalent to a tiny current loop which is capable of producing a magnetic field and hence atom has a magnetic dipole moment. Continue reading “Reason of magnetic effect in magnetic materials”