What Are Electromagnets Used For in Everyday Life?

Electromagnets are magnets powered by an electric current. They consist of a coil of wire. It's often wrapped around a magnetic core made of iron or some other ferromagnetic material. The electromagnet only emits a magnetic field when the current is turned on. The magnetic field can be made stronger or weaker, or it can even be reversed by varying the amount of current that goes through the device.

Function

Electromagnets are primarily used to move things and to store information. They are used to move things because a magnetic field will physically repel iron and certain other materials. By carefully controlling the amount of current a magnet receives, an engineer can control how much force the magnet exerts and how much the target moves. Magnets are used to store information because many materials will absorb and store a magnetic field. The field can then be read back by a magnetic reader when the information is needed again. Many mediums--from audiotapes to memory sticks--use magnets in this way.

Types

One of the simplest types of electromagnets is in a type of switch called a relay. When the electromagnet is turned on, it tugs on a small magnetic switch. This closes it. In this way, a small current can turn a much larger current on and off.

Another common use of electromagnets is in actuators. In an actuator, an electromagnet actually does physical work to move something. For example, the electromagnet actually moves the speaker coil in and out within a speaker. In a motor, it spins the rotor around and around.

A rather specialized--yet very common--use of electromagnets is to power a cathode ray tube in a television. High-powered electromagnets power and steer a stream of electrons, causing them to hit the television screen and make it glow.

Finally, electromagnets are used to store information. A computer hard drive has a special, magnetically sensitive plate. By repeatedly turning on and off, an electromagnet can store bits of information on it.

Size

The size of an electromagnet is determined by how much force it has to exert. The electromagnet in a small relay, for example, is a centimeter or less in length. All it has to do is pull a small strip of metal for a fraction of an inch; it is extremely tiny. On the extreme other end are radio towers, which have to be big enough to make magnetic fields that can travel for miles. In between are the magnets in televisions, which are several inches across. Starter motors in cars have to produce a lot of energy, and they can have electromagnets that measure 1/2 foot or longer.

Significance

Electromagnets allow engineers to easily control movement in a way that would be impossible or prohibitively expensive without them. In a relay, for example, a small magnetic coil attracts one terminal of a small metal switch, pulling it closed. There is one moving part, and no gears are involved, making the whole thing simple and cheap to make. There is no other easy way to make an automatic switch. Electromagnets were also the driving force behind the development of modern media and communication. Even today, they power many microphones, most televisions and nearly all speakers...not to mention computer hard drives. Even radio and television transmission towers are essentially nothing but big electromagnets!

Warning

Many electromagnetic devices are very sensitive to magnetic fields. You can easily ruin your television screen, scramble your credit card or erase your hard drive by bringing a magnet too close to it. Keep all magnets far away from anything with a screen or a memory. Some electromagnets are also potentially dangerous to people. Televisions use extremely high voltage electromagnets to power their cathode rays. Do not open one up and muck about inside unless you really know what you are doing!

Resources

• How Do Electromagnets Work