You may hear many times the word magnet, `around 800 BC ago the people of Asia Minor found a stone-like substance in Magnesia.
It was able to attract small pieces of iron and showed a particular direction when it was suspended to move freely.
It was named lodestone or leading stone because it was used by ancient Chinese navigators for directive purpose.
Since it was discovered in magnesia, it was named magnet.
Lodestone is a natural magnet having a mineral we call it magnetite.
Magnets are those bodies that can affect magnetic bodies.
We also use man-made Magnets.
They are available in many shapes.
Magnets show some particular properties. We say such properties as magnetism.
Properties of magnets
- a magnet attracts magnetic bodies. The attracting force is more at poles than in the middle of it.
- A magnet suspended freely adjusts in north-south direction when it is at rest.
- You cannot separate magnetic poles of a magnet by breaking it into pieces.
- A magnet transfers its magnetic property to other bodies that are in contact with it or near it. The process is magnetic induction.
- Like(N with N, S with S) poles of a magnet repel and unlike( N with S, S with N) poles attract.
Molecular theory of magnetism
The process of making a magnet is called magnetization and the process of losing magnetic property is called demagnetization.
The molecular theory of magnetism explains the mechanism of magnetization and demagnetization of magnetic bodies.
It states that a magnetic body consists of magnetic molecules or molecular magnets.
Each magnetic molecule has S and N poles as in a magnet.
Because of this reason, magnetic poles of a magnet cannot be separated.
Arranging these magnetic molecules in the form of a near chain or ring form in magnetic bodies.
They lose their magnetic force by attracting each other.
The body gets demagnetized but when the magnetic molecules are arranged in the form of an open-chain the body gets magnetized.
At the poles of a magnet, magnetic molecules do not lose their magnetic force by attracting the opposite poles.
In the middle, the magnetic molecules lose their force by attracting each other.
Therefore, a magnet has more magnetic force at the ends than in the middle.
Magnetic field is the area around a magnet up to which it can affect.
We can represent the magnetic field by lines of force. The direction of the magnetic force from N to S is also on the lines of force.
Evidence(proof) for the molecular theory of magnetism.
- We cannot separate the poles of a magnet.
- We can only change the magnetic body into a magnet.
- We can demagnetize a magnet by hammering and heating.
- A magnet has more force at poles than in the middle.
When we keep a magnetic body in contact with or close to a magnet, it shows the magnetic property or it gets magnetize.
The process is magnetic induction.
By this process, the magnetic property until it is close to the magnet.
The end of the magnetic body close to the magnetic pole forms an opposite magnetic pole.
It means that the end of the magnetic body close to the north pole of a magnet forms a south pole and vice versa.
The process of losing its magnetic property by a magnet is demagnetization.
he main cause of demagnetization is the disturbance in the chain of molecular magnets in a magnet. rearranging molecular magnets in a magnet in the form of near chains, the magnet gets demagnetize.
We can demagnetize a magnet by the following activities,
- By dropping the magnet
- By heating the magnet
- By storing the magnet without using keepers
- By rubbing similar poles of the magnet
- By hammering the magnet.
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