Electromagnet

Description
Electromagnets are a type of magnet that can be made by wrapping a nail or other iron rod with wire. The magnetic field in electromagnets is created by electric current aligning domains the the wire. The strength of the magnetic field, therefore, can be controlled by the amount of electric current applied.

Making Electromagnets
RadioShack sells some enamel coated wire that is excellent for making electromagnets. The package has three different gauges in it. Chose your gauge and do the wrappings. Make sure to leave a fair bit of extra wire on the ends. When you finish you will need to sand off some of the enamel on the two ends so that you have a contact surface. You can use simple insulated wire too, but the insulation may melt at lower temperatures than the enamel would and you won't be able to put your wraps as close together.

Uses of Electromagnets industrially
This list has been copied from Wikipedia.
 * Motors and generators
 * Transformers
 * Relays
 * Electric bells and buzzers
 * Loudspeakers and earphones
 * Actuators
 * Magnetic recording and data storage equipment (tape recorders, VCRs, hard disks)
 * Particle accelerators
 * Magnetic locks
 * Magnetic separation of material
 * Industrial lifting magnets
 * Electromagnetic suspension for MAGLEV trains

Uses of Electromagnets for Science Olympiad

 * Mission Possible
 * MagLev