Static on my TV screen

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paul.fr

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Static on my TV screen
« on: 23/04/2008 14:13:15 »
how and why does it get there on CRT TV's, and why is it not there on TFT Flat screens?

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Offline LeeE

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Static on my TV screen
« Reply #1 on: 23/04/2008 16:06:37 »
Do you mean the electrostatic charge that builds up on a crt or the 'snow' stuff that's displayed upon it?
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!

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Offline techmind

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Static on my TV screen
« Reply #2 on: 23/04/2008 22:38:04 »
how and why does it get there on CRT TV's, and why is it not there on TFT Flat screens?

If you mean the static electricity - it feels charged, you can "stick" a piece of paper to it, and it crackles when you move your hand/finger near it, then...

A CRT fires an electron beam at the screen with a charge of 25kV (for a colour TV - somewhat less for black-and-white). Not so surprisingly this tends to cause the glass to become charged. I don't know much more detail than that.

An LCD screen works at very low voltage, maybe -10/+30V maximum - so you won't get any static electricity. Every pixel on a TFT LCD screen contains a tiny thin-film field-effect transistor ... and these are easily damaged by static electricity - much care goes into the design of the screen and especially the factory that makes them to ensure they don't get exposed to damaging static!
"It has been said that the primary function of schools is to impart enough facts to make children stop asking questions. Some, with whom the schools do not succeed, become scientists." - Schmidt-Nielsen "Memoirs of a curious scientist"

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lyner

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Static on my TV screen
« Reply #3 on: 23/04/2008 23:36:27 »
It's charging by electric induction due to the high energy electrons hitting the other side of the glass. AFAIK there is no actual conduction of electric current  through the glass. The energy for the spark you can get from the face of a crt is supplied by the movement of your hand.