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Re: charged parallel plate capacitor

Leakage is unavoidable. That's how cosmic rays were discovered.
Even a very "hard" vacuum has lots of atoms. Cosmic radiation
ionizes some of the atoms. The ions flow to one of the plates, making a
leakage current.
The next step was to fly such a chamber in a balloon and discover
that the leakage current increased with altitude.
Regards,
Jack



On Wed, 27 Feb 2002, Brian Whatcott wrote:

At 10:52 AM 2/27/02, you wrote:
If there were a vacuum between the plates would the charge leak or would the
capacitor be able to hold the charge? Is there such a thing as a capacitor
with a vacuum between the plates?

Thank you.
Kate Farrell-Gray
Amherst HS, Amherst, NY

There are five leakage sources to consider
1) the insulating mount for the plates - if glass, this always carries a
film of water much to the disgust of expermentalists who wish to measure
the weight of glass containers accurately. They cannot - wirthout precautions.
2) the vacuum is no impediment to electron flow if it can be released from
a plate,
by high field emission from a very sharp asperity
3)...by low work function (rare earth) oxide layers warmed suitably.
4)...by energetic radiation a la Geiger (Do Geiger Muller tubes usually
have gas fill to enhance current by avalanche conduction? I can't remember...)
5)...by light radiation of suitable wavelength a la Einstein.


Brian Whatcott
Altus OK Eureka!


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