|MadSci Network: Physics|
I don't know much about CRT's but there are magnetic components in there that retain some permanent magnetic moment if exposed to a large field. This creates small stray fields which exert a force on the electrons and diverting them from their proper paths. This distorts the image. The time the field is appled has no bearing on the "damage" done. The problem is easily corrected by "degaussing" the CRT. This is done with a special device or a large (18 inch diameter) coil with several hundred turns plugged into the wall. Don't leave it plugged in too long!! It will get hot!
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