Make an Electromagnet in Class

Anytime an electric current flows through a wire there is a magnetic field generated around the wire. It is better to use a regular C of D size battery for this purpose in a classroom. Larger batteries would work but pose significant dangers. For example a car battery could explode and could be severe enough to kill a person. The acid inside the battery could also cause blindness. The wire used could heat sufficiently to cause burns and/or catch on fire. A teacher may want to purchase a C or D size "battery holder" at an electronics store which makes the making of an electromagnet much easier. Use a roll of insulated wire that has a diameter about the size of a heavy paper clip, but not nearly as heavy as a typical pencil.

If a length of wire of about 3 feet is used, it would be stripped of insulation at each end for about 1/2 inch. One end of the wire would be attached to the negative side of the battery and then about 7 or 8 inches from this the wire would be tightly coiled around a 10 penny nail (approximate size) and then the other end would be touched to the other side of the battery. The reason for just touching it to the other side of the battery is to keep the wire from getting overly hot and to keep the chance of the battery exploding to a minimum. The longer this stays connected, the hotter the wire could become and the faster the battery would wear out.. Some electronics stores also have switches that can be put into the circuit and can be used to turn on and off the electromagnet.

The nail becomes an electromagnet as the current passes through the coils and causes the iron in the nail to line up differently in the direction of current flow. The coils of wire should be uniform, not crossing forward and back on top of each other. Students are often asked to consider how the electromagnet could be made more effective. They might be asked if a larger nail, more coils, or a larger battery would make a difference. This type of electromagnet should be able to pick up a paper clip and perhaps two paper clips at the same time. When the battery is disconnected the magnetic ability should stop, but there may be some residual magnetic properties now still left in the nail. It may not be enough to pick up a paper clip, but it may be enough to move the needle on a compass.

An electromagnet can disrupt a television or computer monitor, can erase magnetic data, can affect heart pacers, affect other electronic equipment such as watches, calculators, cell phones etc. In the classroom today all of these things that could be damaged by an electromagnet make the construction and use of any type of magnet something to carefully consider.

A needle can be "magnetized" by stroking the needle in one direction 30-60 times with an existing magnet (one side) by a stroke and then you would take the magnet off the needle, move it to the original start of the stroke and then stroking the needle again. You would do this a number of times and the needle would become magnetized. It now could be place on top of a cork floating in a bowl of water and it would align itself in a north / south direction. If you place a few drops of oil in the bowl of water it will help to keep the cork floating more toward the middle of the bowl.

Electromagnets are used in junk yards to move large piles of iron. A special type of electromagnet that vibrates the position of the magnetic field can be used to erase video tapes and cassette tapes. The vibration changes the direction of the magnetic field rapidly mixing up any electronic data on the media. The graphic shows a worksheet that I used to teach about electromagnets in the classroom.

One great experiment that I saw another teacher use was to have a small chimp doll at one end of the room held up near the ceiling by an electromagnet. The wires from this ran completely to the other side of the room, to a battery and then to a rubber dart gun. The dart was where the wires touched together making a type of switch. When the dart was fired at the doll, the switch would open and the doll would fall. The dart would fly toward the doll, but would follow a ballistic curve which caused it to fall toward the Earth at the same rate as the doll would fall toward the Earth. The dart then would be able to hit the doll if it had been aimed correctly to start, .