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Tesla's capacitors




From: 	Richard Quick[SMTP:richard.quick-at-slug-dot-org]
Sent: 	Saturday, September 13, 1997 4:06 PM
To: 	tesla-at-pupman-dot-com
Subject: 	Tesla's capacitors

Quoting Michael Smith [SMTP:md.smith-at-usa-dot-net]

> I have been curious what information about Tesla's capacitors 
> is known. How did he, and from what materials did he construct
> his caps, back in the days before all these groovy materials 
> were available. 

Actually the group missed another obvious answer here. Tesla
patented two capacitors: ELECTRICAL CONDENSER, Patent No. 464,667
Dated Dec. 8, 1891; ELECTRICAL CONDENSER, Patent No. 567,818,
dated September 15, 1896. 

The text of Patent No. 464,667 is especially insightful: 

 I have found that insulating material such as glass, mica, and,  
 in general those bodies which possess the highest specific       
 inductive capacity are inferior as insulators in such devices    
 when currents of the kind described [high frequency, high        
 voltage] are employed to those possessing high insulating power, 
 together with a smaller specific inductive capacity, and I have
 also found that it is very desirable to exclude all gaseous      
 matter from the apparatus, or any access to the same to the
 electrified surfaces, in order to prevent heating by molecular
 bombardment and the loss or injury consequent thereon.  I have 
 found that I may accomplish these results and produce highly
 efficient and reliable condensers by using oil as the di-
 electric, and in this my invention resides.

I have a suspicion, despite the general consensus, that Tesla in
fact used oil capacitors for much of his coil work in New York. 
It is quite true as stated here previously that Tesla employed
micas for his small demonstration coils sets, he also used
commercial micas as "standards" against which he compared the
vaules of his own capacitors.

Colorado Springs more or less forced him into using the less
efficient brine/glass capacitors because of time and financial
contraints.

Richard Quick


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