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I was doing an experiment with my CRT TV where I put aluminum foil on the screen wire it to a can and open the TV and a ring between 2 can will swing if I ground the other can. Anyway I tried something out, I used the same way to charge a metal sphere while the tv was on, the sphere was charged and everything seemed to be alright only when removed the wire (connecting the sphere and the foil) from the foil on the TV the sphere lost its charge, why is that? If the charge just decayed, is that normal to decay so fast (in less than a minute) while it is not grounded?

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There is quite a nice article on charge decay here. It's hard to comment of the mechanism of charge decay in your experiment without knowing the experimental details. Unless it was very humid I'd guess the sphere wasn't as insulated as you thought and the charge was leaking through whatever was supporting the sphere.

There's a description of the effect of humidity here. The major effect is that at high humidity you get a thin layer of conducting water on surfaces. In addition to this a lot of biologically derived materials (e.g. cotton) absorb water from the air and this increases their conductivity.

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The details about the experiment is in the link above in the description. The sphere was above the TV , do you think this is cause the problem ?About the article in your answer about the charge decay , all the plates are grounded , my sphere isn't. – Abdelrahman Esmat Dec 24 '12 at 14:36

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