All electromagnets generate magnetic fields, and you can build an electromagnet with some simple items from the hardware store. Fundamentally, electromagnetic fields are produced when a current is run through a solenoidal coil of wire, in a shape similar to a common metal spring. The very motion of the electrons travelling through the wire is what creates the magnetic field. The field can be strengthened if the wire is coiled around a cylindrical metal object, such as an iron nail.
Place your materials on a nonconducting surface, such as wood or concrete.
Coil the copper wire as tightly as you can around the iron nail. Start by the head of the nail and wrap the wire round and round until you reach the tip of the nail. The more coils you make, the stronger your electromagnetic field generator will be. Clip the copper wire so there are short leads coming from the head and point ends of the nail.
Connect one end of a piece of insulated wire to the copper lead coming from the head of the nail. Connect the other end of the insulated wire to one of the electrodes on the variable power supply.
Connect one end of a piece of insulated wire to the copper lead coming from the point of the nail. Connect the other end of the insulated wire to the other electrode on the variable power supply.
Place a few paper clips near the nail as it lies on the surface where you are working.
Set the dial on the variable power supply to 0 Volts. Plug the power supply in and turn it on. Slowly turn the voltage dial up and watch the paper clips. You will see them react to the magnetic field from the nail as soon as it is strong enough. Expect a reaction at a relatively low voltage, perhaps 0.5 to 1.5 volts.
Do not touch the nail while the power supply is turned on.