How Does a Demagnetizer Work?

From industrial manufacturing to the workbench, demagnetizers (also called degaussers) have a variety of uses. A demagnetizer is an electric solenoid, or coil, powered by alternating current. The current produces a magnetic field. The key to the demagnetizing action is that the magnetic field strength and polarity alternates, just like the current.


Iron objects have tiny pockets of magnetism, called domains, but they’re usually disorganized, and the domains cancel each other out. If something has a noticeable magnetic field, it means the domains organize so that they add up. A demagnetizer will randomize or scramble the domains of a magnetized object when it moves near the alternating magnetic field. It still has magnetized domains, but since they’re no longer lining up the same way, they cancel each other out.

Industrial Demagnetizers

Magnetism can build up on metal parts during manufacturing. Industrial demagnetizers remove this magnetism. Though larger than other demagnetizers, they use the same basic principles. An industrial demagnetizer may be a large box or tunnel through which parts pass on a conveyor belt. The demagnetizer may have warning signs to alert you to strong magnetic fields that might affect pacemakers, credit cards in your wallet, or other metal or magnetic items.

Hand Tool Demagnetizer

Bench and tool demagnetizers remove magnetism that builds up on metal hand tools. Some of these small demagnetizers are AC powered; some use permanent magnets.

Audio Demagnetizer

In cassette and open-reel tape players, audio tape leaves residual magnetism on the metal parts inside. This magnetism builds up over time. Recordings becoming noisier and the music on the tape gets slowly erased. Special demagnetizers remove the magnetic build-up, and alleviate this problem.

Data Demagnetizer

Data demagnetizers erase the data from tapes and disk drives. When old computers are retired, the data should be wiped from the hard disk so private or proprietary information won’t make its way through the salvage market to another user. A powerful demagnetizer is one way to do this. Similarly, audio and video media demagnetizers can wipe audio and videotapes clean for re-use.

CRT Degausser

CRT-type computer monitors and televisions have a demagnetizer built into the screen. The CRT uses magnetic fields during operation that build up on some metal parts. If the magnetism is allowed to build up, the image will become fuzzy and distorted. The degausser works automatically when you turn the CRT on. You can usually run the degausser from a set-up menu also.

About the Author

Chicago native John Papiewski has a physics degree and has been writing since 1991. He has contributed to "Foresight Update," a nanotechnology newsletter from the Foresight Institute. He also contributed to the book, "Nanotechnology: Molecular Speculations on Global Abundance." Please, no workplace calls/emails!

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