Nirmal Singh.
Last Activity: 10 Years ago
This only works on old fashioned tv screens or
computer monitors, so to understand why this happens we need to know how
they work. Inside a television there is a big glass chamber which has
had all the air sucked out to make a vacuum. At the back of this
chamber is an electrical gun which fires electrons towards the back of
the screen. The screen is covered with tiny lumps of phosphor, which
glows when an electron hits it. If you cover the whole screen with one color of phosphor, you get a black and white tv.
To make a color tv screen, they put tiny spots of
three different colors of phosphor on the screen in groups. Each group
contains a spot of red, a spot of green and one of blue. Lighting
these up in different combinations can make all the colours you see on
your tv.
As electrons fly towards the screen, they can be
moved using a magnetic field – this lets you aim the electrons at the
right spot of phosphor and get the right colours in the right place.
When you put a magnet near the tv, it diverts the
electrons away from where they should go, and so the wrong phosphor
spots light up and you don’t get the right colours.
Sometimes, if you put a magnet near a tv for too
long, you can make bits of it magnetic and so it will always distort the
colours, thish is how the colours stay there.
Some tv’s have a degaussing coil inside them that
re-sets the magnetism when you switch them on, so the colours go back to
being correct.
Thanks & Regards,
Nirmal Singh
Askiitians Faculty