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# Magnetism

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 Sub Topics Magnetism is a physical phenomena which includes the force of attraction between two magnetic objects. This arises due to the magnetic field present around the object. Magnetism is an inherent property of certain material which are known as magnets. Magnets play a dominant role in modern life, as we know a vast number of devices are employed in the electromagnetic industry.

## What are Magnets?

Magnet is a material which produces a magnetic field. There are two types of poles present in a magnet, north pole and south pole. North-north pole repels each other whereas north-south pole attracts each other.

As mentioned earlier, magnetism is an inherent property of magnets. So we can say that, magnetism is an attractive or repulsive force between two magnetic poles.

## Types of Magnets

Main types of magnets are listed below :

Permanent magnets :
It possesses magnetic properties once it is magnetized. And it has permanent magnetic moment.
Example : Alnico, ferrite

Temporary magnets :
This type material shows magnetism when it is placed in a magnetic field. After removing the field it lost their magnetic effects.
Example : Iron

Electromagnets :
These materials shows magnetism if an electric current passes through it. These magnets are in the form of solenoids.
Example : Steel

## Magnetic Properties

Magnetic properties are classified as diamagnetism, paramagnetism and ferromagnetism.

Diamagnetism : When a material is subjected to an external magnetic field a current is flowing through the material. This current is responsible for align the magnetic dipole in such a way that it should be in the opposite direction of the applied. These type materials are known as diamagnetic materials.
Example: Superconductors

Paramagnetism : In the case of paramagnetic materials, the materiel is attracted by the external applied field.
Example: Most of the chemical compounds

Ferromagnetism : Ferromagnetic substances posses its property until some temperature beyond that temp. it lost its property and become paramagnet. This maximum temperature is known as the Curie temperature.
Example: Iron

## Magnetic Force

Magnetic force is nothing but the force between the two electrically charged moving particle. In other words, it is the force between the two poles of magnet which produce magnetization. The force between north-north pole is repulsive in nature whereas the force between south-north pole is attractive one.

## Magnetic Fields

Magnetic fields are like gravitational fields which cannot be touched but can feel the influence of the field. According to gravitational field, we can feel the influence directly. But in the case of magnetic field, it cannot measure directly.

We can realize the presence of magnetic field by checking the magnetic properties governed by some materials. In some cases, electric current produce the magnetic filed. These type magnets are known as an electromagnet. Further details about the electromagnets are given below.

## Magnetic Field Strength

The amount of the magnetic flux through a unit area is termed as the magnetic field strength.It is denoted by H and the expression is given by,
H = $\frac{B_{0}}{\mu _{0}}$
where,
$B_{0}$ is the magnetic field
$\mu _{0}$ is the permeability

## Magnetic Dipole

Two poles of a magnet is separated by small distance which is termed as magnetic dipole. In the case of a magnet, mono pole do not exists. The moment of this dipole is known as magnetic dipole moment. It is expressed as,
P = IA
where,
I is the current
A is the area