The Demonstrations: We have several electromagnets including the Jumping Ring, the Can Crusher, and the battery-less flashlight.
The Physics:
Electricity and magnetism are very closely related. This is
dramatically demonstrated by the electromagnet. An electromagnet is a
magnet made with electricity. Normal magnets are called permanent
magnets. An electromagnet has the same properties as an ordinary
magnet. It has a north and south pole and it attracts steel and iron.
It is different from a permanent magnet because it can be turned on and
off.
When electricity flows in a circle of wire, it makes a magnet. One side
of the wire is a north pole, the other side is a south pole. If there
are many loops of wire, the magnet is stronger.
The way to make a simple electromagnet is shown in the drawing. All
that is needed is a long piece of steel, like a big nail, some
insulated wire and a strong battery. A 1 ½ volt D cell is good.
(A car battery is too strong.) The magnet is made by winding the wire
around the nail very tightly. The more windings, the stronger the
magnet, but be sure to leave the ends free. Make only one layer of wire
on the nail. Hook up the ends to a battery. Make sure that you get a
good connection between the wires and the battery. Now you can pick up
paper clips, staples, and even other nails. Try using a permanent
magnet to find the north and south poles of the electromagnet. When you
disconnect the battery, the electromagnet is turned off. The nail may
still be a bit magnetized, but it will soon wear off. Don’t leave the
electromagnet on for too long; it will quickly get hot and drain the
battery.
