Jarrod Taylor, of Balclutha Primary School, asks :-
How do magnets work?
John Campbell, a physicist at the University of Canterbury, responded.
Magnets are a result of electrical currents. You can show this effect if you have a magnetic compass, some copper wire and a torch battery. To make an electromagnet wind part of the wire into a coil of several turns of diameter about the same size as the compass. Place this on its edge near the compass and briefly touch the two ends of the wire on opposite ends of the battery. You should see the compass needle move. (Dont leave the wire connected to the battery too long or it will run out of energy.) By altering the orientation of the coil with respect to the compass needle you will soon learn that the orientation which gives the biggest effect is when the axis of the coil is at right angles to the end of the compass needle.
So there are many devices, such as electric motors, which use magnetic forces to operate. However, there are some materials which are permanently magnetised such as an iron magnet. Where does their magnetism come from? From the electrical currents of electrons orbiting the atom.
An atom is a tiny thing. It would take about five million side-by-side to cross a full stop on this page. Every atom consists of an even tinier nucleus, as first shown by our countryman Ernest Rutherford, about which orbit very tiny electrical particles (electrons). So each orbiting electron is a little electromagnet. Because of the way electrons pair up in atomic orbits and chemical bonds the magnetism of one electron cancels that of its pair. They circle in opposite directions. So usually atoms dont show strong magnetic effects. Atoms with an odd number of electrons must behave like a little magnet. However, in almost all atoms each atom's magnet points in a different direction and overall they cancel out. There are a few materials, such as iron, colbalt, and gadolinium, for which the atoms all cooperate and point in the same direction. For these materials, often called ferromagnetic materials, each atom has a very tiny magnetic effect but because there are so many atoms all co-operating (about 100,000,000,000,000,000,000 atoms in a pinhead) the resulting magnetism is very strong.