Electronics Questions: How Electromagnets Work

Learn how electromagnets work, what they are composed of, and what they are used for.

An electromagnet is just like any other magnet and will attract certain metals (iron and steel) and other magnets. The difference is an electromagnet only works when electricity is flowing through it. So what components make up an electromagnet and how does it work? In this article we will answer those questions as we look at how electromagnets work.

A note about magnets

Recall that regular magnets have two magnetic poles, north and south. Like poles repel and opposite poles attract. So the south pole of one magnet would attract the north pole of another magnet but two south poles would repel. The magnetic field of an electromagnet acts the same as a regular magnet except the poles can be reversed by switching the flow of electricity (change the positive and negative terminals to the power supply). This comes in handy when creating electric motors, speakers, and solenoids.

Parts of an electromagnet and how they work

First we must understand a little bit about electricity. Every time electricity flows through a wire, electrons are in motion and a small magnetic field is generated. This magnetic field is like an imaginary ring around the wire. One way to increase the size of the magnetic field generated is to coil the wire. With wire coiled on top of itself, the small magnetic field builds with each successive layer of wire to produce a large magnetic field.



Electromagnets consist of wire coiled around a core. The core can be anything from air to a nail or even a pencil. Since electrons flow freely through a conductive core (like a nail), an electromagnet made with a metal core will have a larger magnetic field (and thus be stronger) than an electromagnet with a wooden core. The strength of an electromagnet is related to the number of times the wire is coiled around the core and the distance the wire covers across the core. The more coils wrapped closer together, the stronger an electromagnet will be. The amount of voltage running through the wire also plays a role in an electromagnet's strength. More voltage means more electrons moving through the wire and thus a stronger magnet.

Since an electromagnet will not work without electricity, we also need a power source such as a battery. The power source provides the electricity to charge an electromagnet into action. Power runs through the wire, around the coil, and back to the battery to produce the magnetic field.

Disconnect the battery and the electromagnet no longer functions. If the battery is reconnected with the positive and negative terminals reversed, current will flow through the wire in the opposite direction. This results in a switch of the magnetic poles in the electromagnet. Metal objects or other magnets can be moved back and forth (attracted and repelled) by repeatedly switching the poles of an electromagnet.

Why an electromagnet works

As stated previously, electromagnets need electricity to work. The wire coil wrapped around a core means that millions of electrons are flowing in a small space. As the electrons flow through the wire, other electrons around them and in the core are excited and begin moving. The result is a magnetic field that grows until electricity is flowing freely through the coil. At this point the electromagnet has "charged up" and is producing its maximum magnetic field.

Electromagnets store electricity

It wasn't a mistake to say the electromagnet has charged up. After power is disconnected from the electromagnet, electrons continue to move as the magnetic field collapses. The electrons are discharged out the end of the electromagnet and produce a short supply of electricity after the power source is turned off. Not only can electromagnets function as magnets, they function as crude electric storage devices too. The magnetic field collapses quickly so the time and amount of electricity produced during the collapse is minimal. Even though electromagnets have no practical use in storing energy, it is important to note that they store electricity for a short time after the power supply is turned off.

Uses for electromagnets

Electromagnets are used in equipment all over the world, even many household items. Fans, speakers, and refrigerators all use electromagnets. Cars and trucks also use electromagnets to control things like cooling fans and power door locks. One major accomplishment of the electromagnet is an electric engine. A cylinder is lined with electromagnets and used to spin an electromagnetic shaft in the center. A similar design using electromagnets is found in a solenoid. A solenoid is like an electric engine except instead of spinning a shaft in the middle of the cylinder, it uses the magnetic field to move the shaft in and out. This is the device used on most power door locks.

No matter what electromagnets are used for, they have advanced technology and made the impossible seem a little bit closer. From science experiments to electromagnet-powered cars, electromagnets are an amazing accomplishment and a great benefit for all.

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