Magnets are very useful to us. they are an essential part of loudspeakers, microphones electric motors, door bells and many other things. Magnetism was first discovered 2,500 years ago in a stone called lodestone, which people used to make the first compasses. Only the metals iron, nickel and cobalt can be magnetized on their own, but powerful magnets can be made by mixing these with other metals. Steel is iron with a little carbon in it, so it makes strong magnets too. See if you can find a magnet and find out what sorts of things it can pick up.

What is a magnet?  

Imagine lots of matches representing groups of molecules in a magnetic substance. Each matchstick is like a little magnet with a north pole at its head end and a south pole at the other end. A bar of unmagnetized iron can be thought of as jumble of matchstick magnets, so mixed up that all their magnetic forces cancel out. When the iron bar is magnetized, many of the molecular magnets line up, with their north poles pointing the same way. (see diagram below)

unmagnetized iron     magnetized iron

 Make a magnet 

Playing with two bar magnets, you will find that a north pole will attract a south pole. Two "like poles" - south/south or north/north - repel each other. You can magnetize a steel needle by stroking it in the same direction eight or nine times with the north pole of bar magnet. As you do this, the north pole of the magnet pulls the south poles of the tiny molecular magnets in the needle and makes them start to line up. See if the needle can pick things up now. If not, stroke it some more.

 Destroying magnetism

When something is magnetized, many of its molecules are pointing the same way. To destroy magnetism, you need to mix up all the "molecular magnets" again. You can do this by hitting a magnet with a hammer, or heating it until it is red-hot and letting it cool down (don't do this yourself).

 Fields of force

You can't see what makes magnets work, but there are magnetic forces around them and you can see the pattern they make by using iron filings. Put about one teaspoonful of filings into a box and shake it around so they cover the bottom. Hold the box just above a magnet, tap the box and you will see the filings jump up. They fall down into a pattern made up of curved lines. This pattern is called a field of force. These lines of force show what happens in the space around a magnet. Try doing this by clicking on the experiments below:

[Field of magnetic field]      [Attraction & repulsion of poles]


[Make a compass]   [FAQ]  [Interview Mr. Magneto]  

[You can make a magnetic field that's stronger than the earth's]


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