The effects of a strong magnet on a TV screen

Written by j.t. barett
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The effects of a strong magnet on a TV screen
Television Set (Image by, courtesy of hobvias sudoneighm)

The Cathode Ray Tube (CRT) that all TVs used can be damaged by strong magnets. A part inside the tube can accumulate a magnetic field, distorting the image. If the magnet is very strong, it can bend this part and ruin the CRT.

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The Cathode-Ray Tube (CRT), or picture tube, was used in all televisions before plasma and LCD screens were introduced. In the CRT, a moving magnetic field guides an electron beam, making a phosphor screen light up with an image.

Shadow Mask

Inside the CRT screen, a metal grid called the shadow mask can gradually become magnetised. If it does, the magnetism will interfere with the electron beam and the TV picture will become distorted.


The shadow mask's magnetic field can be removed with a device called a degausser. Better TVs had degaussers built in, so the picture never becomes distorted.

Strong Magnet

A very strong magnet placed on the TV screen might permanently magnetise the shadow mask or even bend it. If this happens, the CRT may have to be replaced.

LCD and Plasma TV

Flat-screen LCD and Plasma TVs don't use electron beams or magnetic fields. They are immune to the effects of a strong magnet.

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