Magnetism is an unseen force that attracts iron, nickel, and cobalt; the only three substances in the World that can become magnets. These materials are called ferromagnetic substances. Metal such as iron is a 'soft' ferromagnetic material, and any magnetism induced when placed on a magnet, would quickly decay when removed. Alloys of these substances can be formed into a 'hard' ferromagnetic material, which can be used to produce permanent magnets.

Magnets of whatever shape, have a north-seeking pole (north pole) and a south-seeking pole (south pole).The term seeking is used because they actually seek the Earth's north and south poles. One confusing fact is, that although we use a compass to point to the north, in reality, because the poles are reversed, the needle is actually pointing to the Earth's south magnetic pole. The nature of magnets are that similar poles repel and opposite poles attract. that is if you had two magnets the north pole of one would pull towards it, the south pole of the other, and if these were fairly strong magnets, you would not be able to pull them apart without twisting them and breaking the lines of force. On the other hand, if you tried to push the north pole of one against the north pole of the other, you would feel the strong opposition, and again if they were fairly strong magnets, you would find it impossible to push them together.

Magnetic lines of force never cross, but always form complete loops.

Electromagnets

Magnets made with electric current are called electromagnets. Electromagnets are temporary magnets. They can be turned on or off. An electromagnet is simply a coil of wire. It is usually wound around an iron core. However, it could be wound around an air core, in which case it is called a solenoid. When connected to a DC voltage or current source, the electromagnet becomes energized, creating a magnetic field just like a permanent magnet. The magnetic flux density is proportional to the magnitude of the current flowing in the wire of the electromagnet. The polarity of the electromagnet is determined by the direction of the current.

You can make your own electromagnet, with only a nail, wire, and battery:

Wind the wire around the centre two-thirds of the nail, leaving suffcient wire at each end to reach your battery.Affix the wire to the nail with some tape, to avoid it falling off in use.

Strip off the insulation from the wire at both ends, and fasten on end onto the battery + connector.

Hold the other end of the wire onto the battery - connector, while holding the nail over some paper clips, demonstrating it's magnetic abilities.

The strength of the electromagnet can be increased by increasing the number of wraps in the coil or by increasing the voltage of electricity in the coil.

Don't leave it connected too long, as the battery will drain very quickly.

WARNING: Do not place electromagnets near computer disks, VCR, audiotapes, televisions, or computer monitors. If the wire or battery becomes hot, disconnect the wire.

The Earth is a huge magnet, with it's magnetism extending into the magnetosphere, an area around the Earth that is made up of positively charged protons and negatively charged electrons. Magnetic field lines radiate between Earth's north and south magnetic poles, just like the poles of a bar magnet. Charged particles are trapped on these field lines, forming the magnetosphere. While the field lines of a bar magnet are symmetrical, the effect of the constant stream of high energy particles from the Sun (the solar winds) compresses the field lines facing the Sun, and the field lines away from the Sun stream back to form the Earth's magnetotail.

The magnetosphere extends into the vacuum of space from 80-60,000km on the side facing the Sun, and tails out to over 300,000km away from the Sun. This magnetic field protects us from the worst of the harmful effects of the solar winds. A great deal of the matter in the solar winds is deflected around the Earth by the magnetosphere. These high energy particles would 'singe' the earth's atmosphere, but for this protective magnetic field. Many of the remaining particles given off by the Sun, are concentrated into layers called the Van Allen belts.