Magnetism

Magnets are fascinating!

In comic books magnetism is turned into an awesome power to possess. (See Magneto on the right...)

We love magnets and gadgets that use them.

Magnetism is linked with the idea of mystical powers - putting things under the 'fluence - moving things by an invisible force - making things float. It is amazing!

Click here to find out about floating frogs (because of the use of magnetism!)

We use magnets for so many things, even 'health aiding' jewelery.

 

Lessons on magnetism are always great fun.

But take care and listen to the teacher's instructions - especially when working with iron filings.

Iron filings easily become magnetised and stick to each other, surfaces and your skin...

If you rub your eyes when you have iron filings on your fingers you can easily get the tiny sharp metal pieces in your eyes. They can tear or pierce the cornea.

If that happens you need to go to an emergency room! The doctors will use a magnet to extract the filings before any more damage is done.

The Magnet - 'naming things' (the scientific terms you need to know)

The end of a magnet that attracts iron objects to it is called the 'pole'.

A magnet has two poles - the NORTH pole and the SOUTH pole. If freely suspended it will orientate itself so that the end called the North Pole points north. This is why it is called the North Pole - it seeks out the north.

See the page on the Earth's Magnetic field

There are three 'magnetic elements': iron, nickel and cobalt. Only these and their alloys (mixtures of metals containing them) will be attracted to a magnet... all other metals will not.

The domain theory

The Domain Theory aims to explain why metals get magnetised. You need to think of the magnetic elements having little molecular magnets inside them. These are randomly orientated in an unmagnetized piece of metal but point in a particular direction in a magnetised piece.
 
 

Soft magnetic materials (e.g. iron) have domains that easily move into line when the metal is placed in a magnetic field but as soon as the field is removed the domains take on a random pattern again. It returns to being unmagnetized straight away. very little energy is required to magnetise a soft magnetic material

Hard magnetic materials (e.g. steel) have domains that do not easily move into line when the metal is placed in a magnetic field, a strong field is needed for some time, but then, when the field is removed the domains retain the magnetic pattern. The metal stays magnetic for a long time. A lot of energy is required to magnetise a hard magnetic material. That energy is changed into heat within the material during the magnetism process.

The compass - field line patterns and using plotting compasses - click here

Making and destroying magnets - click here

Click here to see the magnetism related topics split into keystages and links to suitable questions set for those levels of understanding. The questions have worked solutions and hints on good examination technique.

Try the magnetism wordmaze - click here

Magnetism and levitation - click here

Now take a look at Electromagnetism....