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Permanent Magnets And Magnetic Behaviour

Permanent Magnets

The magnetic field is produced by objects known as magnets. When these properties of magnetism are not lost throughout time it’s known as a permanent magnet.

Magnetism is shown by ferromagnetic material as well. Some materials are a few alloys of iron and nickel. The way the domains are oriented in a ferromagnetic substance depends on the property of magnetism.
The magnetic fields that are produced individually cancel themselves out when the domains are randomly oriented. A collective magnetic field can be produced by reducing the randomization of the domain by influencing it by an electrical field. This is one of the processes through which electromagnets are produced. But if the domains are already arranged such that they point in the same direction, even without an external influence they will produce a collective magnetic field. These are permanent magnets.

Magnetic Behaviour

When imposing a magnetizing field on ferromagnetic substances the domains get arranged to produce magnetism and do not go back to their normal state. When the driving field is zero and even then the domains have not rearranged themselves to normalcy the time the substance takes to demagnetize or remains magnetised for is known as remanence. If we try to put the magnetic property back to zero by applying a field in an opposite direction the amount of that reverse field that’s required to demagnetise that substance is known as coercivity. The lack to retain the magnetic property of a substance is known as hysteresis.

Have you ever noticed that an iron nail which has been attached to a magnet for some time attracts other non-magnetic iron nails for a short span even after it has been detached from the magnet? This is because the domains of the iron nail had been reoriented. This effect is weak and is lost pretty soon. Therefore, an iron nail will not be considered as a permanent magnet.

The main advantage of a permanent magnet over any other type is that it does not need a continuous supply of external energy (in the case of electromagnets, electricity) to exhibit magnetism. For example, permanent magnets are used as compass needles.

Permanent Magnet

Example of Permanent Magnets

An everyday example of a permanent magnet is a refrigerator magnet. The image below shows the magnetic field produced by a bar magnet. The magnetic field is the sphere of influence of the magnet.

This can be visualised by sprinkling iron filings on a bar magnet. The filings will arrange themselves on the magnetic field lines of the magnet used. The strength of different magnets can be seen physically in this way.

This can be visualised by sprinkling iron filings on a bar magnet. The filings will arrange themselves on the magnetic field lines of the magnet used. The strength of different magnets can be seen physically in this way.

Frequently Asked Questions – FAQs

What is a magnet?

An object which is capable of producing magnetic fields and attracting unlike poles and repelling like poles.

What are magnetic field lines?

Magnetic field line or lines of forces shows the strength of a magnet and the direction of a magnet’s force. It was discovered by Michael Faraday to visualise the magnetic field.

What is the basic law of magnetism

The basic law of magnetism is that unlike poles attract and like poles repel.

What are temporary magnets?

Temporary magnets can be magnetised in the presence of a magnetic field. When the magnetic field is removed, these materials lose their magnetic property. Iron nails and paper clips are examples of the temporary magnet.

What are permanent magnets?

Permanent magnets are those magnets that are commonly used. They are known as permanent magnets because they do not lose their magnetic property once they are magnetised.
Test Your Knowledge On Studying The Behavior Of Permanent Magnets!

1 Comment

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