Re: Bottle Capacitors

To: "'Tesla List'" <tesla-at-poodle.pupman-dot-com>
Subject: Re: Bottle Capacitors
From: Tesla List <tesla-at-stic-dot-net>
Date: Tue, 18 Nov 1997 22:40:36 -0600
Approved: tesla-at-stic-dot-net

From: 	Alfred A. Skrocki[SMTP:alfred.skrocki-at-cybernetworking-dot-com]
Sent: 	Tuesday, November 18, 1997 12:52 AM
To: 	Tesla List
Subject: 	Re: Bottle Capacitors

On Monday, November 17, 1997 9:28 AM MATTHEW A PRICE
[SMTP:ch038map-at-mode.lanl.k12.nm.us] wrote;

> I am trying to construct a few bottle capacitors and have a few questions.
> Many instruction for bottle caps say to use a bolt for the top terminal.
> Wouldn't a long nail, or thick copper wire work just as good, or better ?

Bolt or nail really makes no difference, the only reason a bolt is typicaly
suggested is because it is easier to install due to it's being threaded.

> does the shape of the bottle effect the capcitance? I would think It would
> slighly...

The formula to calculate a capacitors capacitance is;

        0.224 x K x A
    C = -------------  x (N - 1)
              d

     C = capacitance (in picofarads)
     K = dielectric constant
     A = area of plates (in inches)
     d = seperation of plates (in inches)
     n = number of plates

On bottle capacitors the bottle is the dielectric so its shape effects the 
area of the plates and thus directly effects the resultant capacitance.
 
> Lastly, does any one know a good list of dielectrics and how
> good them are that is on the web?

The best place to look for specs on dielectrics is in the older copies of 
the CRC Handbook (Chemical Rubber Company) and in the older copies of the
Radio Amateurs Handbook by the A.R.R.L. Remember it is not just the 
dielectric constant and dielectric strength of a dielectric that determine
how good a capacitor it will make but the power factor is usualy the final
deciding factor. Power factor is a measure of how much R.F. a dielectric 
absorbs and the larger the power factor the greater the amount of R.F. the
dielectric absorbs and the WORSE a capacitor it makes because the absorbed 
R.F. is lost power taken from the system and wasted heating up the 
dielectric.

                               Sincerely

                                \\\|///
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                           Alfred A. Skrocki
                   Alfred.Skrocki-at-CyberNetworking-dot-com
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