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. So what is this special property in a permanent magnet that is not lost in the test of time?
Have you ever noticed that an iron nail which has been attached to a magnet for sometime 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 that 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.
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 visualized 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 visualized 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.
