Artificial magnets are produced from
magnetic materials. These are generally made by magnetizing iron or steel
alloys electrically. These magnets are also produced by striking a magnetic
material with magnetite or with other artificial magnets. Depending on their
ability to retain their magnetic property, artificial magnets are classified as
permanent magnets or temporary magnets.
1. Temporary Magnets
Temporary magnets are produced with
the help of an external magnetic field. They lose their magnetic property as
soon as the external magnetic field is removed. They are made from soft iron.
Soft iron behaves as a magnet under the influence of an external magnetic field
produced in a coil of wire carrying a current. But, it loses the magnetic
properties as soon as the current is stopped in the circuit. Magnets used in
electric bells and cranes are the examples of temporary magnets.
Spread some steel pins
on a wooden board and bring an iron nail near them. Are they attracted? Now,
make one of the magnetic poles of the bar magnet touch one end of the iron
nail. Slide it along its length in one direction slowly till the other end is
reached. Repeat the process 20 to 30 times as shown in the diagram. The magnet
has to be moved in one direction only. Avoid the swiping of the magnet back and
forth. Now, bring the iron nail near the steel pins. What do you notice? The
steel pins stick to the iron nail because nail has become a temporary magnet.
Magnetisation is a
process in which a substance is made a permanent or temporary magnet by exposing
it to an external magnetic field. This is one of the methods to produce
2. Permanent Magnets
Permanent magnets are artificial
magnets that retain their magnetic property even in the absence of an external
magnetic field. These magnets are produced from substances like hardened steel
and some alloys. The most commonly used permanent magnets are made of ALNICO
(An alloy of aluminium, nickel and cobalt). Magnets used in refrigerators,
speakers, fridge and magnetic compass are some familiar examples of a permanent
magnet. Neodymium magnets are the strongest and the most powerful magnets on
Alnico cow magnet is
used to attract sharp iron wire and other iron objects that may be ingested by
animals while grazing thereby causing damage to their digestive tract.
The magnetic properties of a magnet
will be removed from it by the following ways.
* Placing the magnet idle for a long
* Continuous hammering of the
* Dropping the magnet from a height.
* Heating a magnet to a high
* Passing a variable current in a
coil that encloses the magnet.
* Improper storage of the magnet.