FUN WITH MAGNETS
A mineral was discovered in the town of magnesia which was found to have a wondrous property. It could attract pieces of iron towards it.
This mineral is called magnetite. Further it was found that thin strips of magnetite always align themselves in a particular direction when
suspended freely In air. It was found that magnetite is mainly composed of oxides of iron (Fe30 4). Magnetite (Fe30.) is the world's first magnet.
It is also called natural magnet.
(a) Types of Magnet :
(i) Natural magnet :
A magnet which occurs naturally and is not made by any artificial means is called a natural magnet.
Eg : Magnetite, Which is an ore of iron [Fe3O4].
(ii) Artificial magnet :
A substance to which properties of the natural magnet are imparted by artificial means is called artificial magnet.
Eg : The magnets made from iron, steel, cobalt and nickel.
(b) Properties of a Bar Magnet :
(i) It attracts small pieces of iron towards itself.
Spread out some iron fillings over a sheet of paper. Now, move a bar magnet in the fillings taking care that all parts of the magnet moves
through iron fillings and observe how the iron fillings are distributed all over the magnet. We will notice that most of the iron fillings cling
near the ends of the magnet while there are a few iron fillings near the middle.
Repeat the experiment with a horseshoe magnet. This experiment explains the attractive property of magnets.
(ii) The magnetic pull seems to come from two points near the ends. These preferred regions of attraction are called the magnetic poles.
We will find that all magnets have maximum attractive power at their poles. Poles of a magnet remain slightly inside from the end points. .
(iii) A freely suspended magnet always align itself along the north-south direction.
The end of the magnet that points towards the north is called the north pole (N-pole) and the other end of the magnet pointing towards
the south is called the south-pole (S-pole).
(iv) Like poles of the magnets repel each other while unlike poles attract each other.
(v) Magnetic poles always exist in pair . .
(vi) Repulsion is the surest test of magnetism. Since a magnet can attract magnetic substances and magnet also but it will always
repel the magnet only.
TEMPORARY AND PERMANENT MAGNETS
(a) Temporary Magnets :
The magnets which cannot retain their magnetism for a long time are called temporary magnets. The temporary magnets are made
from the 80ft Iron.
Eg : Electromagnet
(b) Permanent Magnets :
The magnets which retain their magnetism for a very long time are called permanent magnets. The permanent magnets are generally
made from steel. More powerful permanent magnets are made from ALNICO, an alloy of aluminium, nickel and cobalt or from ferrite.
The ferrite made permanent magnets are quite strong.