Question:
What happens to the electrons that bombard the screen of
a television when it is switched on? They cannot just disappear. Only
when the television is turned off and on does the electrons stick to the
outside of the screen. Also, when I switch off my computer screen
electric discharge sounds are heard at the back of the electron gun.
Please comment.
Replies:
You are right in that electrons do not disappear. They move along the back
of the screen through the power supply that is keeping the inside of the
screen at a very large positive voltage (perhaps 25,000 volts) so the
electrons are accelerated toward the screen to cause the correct phosphors
to glow when they strike it. I do not know why there are electric discharges
at the back of the electron gun when your computer is turned off; perhaps
it continues to be charged up with electrons, but the electrons are not
accelerated towards the screen since that voltage may already have fallen to
zero. This could make the gun very negative and the resulting discharges
are the electrons escaping.
NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.
