Re: Elementary Lecture

To: tesla-at-pupman-dot-com
Subject: Re: Elementary Lecture
From: Jim Lux <jimlux-at-jpl.nasa.gov> (by way of Terry Fritz <twf-at-verinet-dot-com>)
Date: Thu, 25 Feb 1999 11:36:35 -0700
Approved: twf-at-verinet-dot-com

Tesla List wrote:
> 
> Original Poster: Brandywine <brandywine-at-writeme-dot-com>
> 
>    Why sparks will leap between the toroid and a grounded object is quite
> understandable; but the magic of a Tesla coil is that sparks spontaneously
> branch
> out into thin air, connecting with seemingly nothing.
>    Consider 2 devices: A million volt Tesla Coil, and a million volt 60 Hz
> transformer. The TC will emit a discharge into the air that connects to
> nothing.
> We'll help the million volt xfmr by grounding one of the secondary HV
> terminals.
> Do sparks spontaneously emanate from the other HV terminal into thin air?
No.

Oh yes they do... Check out any textbook on HV engineering and they'll
have pictures. For instance, Bazelyan and Raizer, "Spark Discharge", CRC
Press, 1998, page 7

The form of the sparks is different looking for the various frequencies,
but that is more due to the pulsed nature of a TC output. A HV DC source
produces a more brushy corona, breaking down into an arc. Tube coils
with stiff DC supplies (i.e. lots of filter C) (which are essentially
steady state HF sources) also produce brushier discharges. 

If the field is high enough (>71 kV/inch, 30kV/cm) the air breaks down.
The shape of the field and the dynamics of the supply current determine
what the sparks look like, etc.

> > 
Jim Lux                               Jet Propulsion Laboratory
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