Re: Streamer Behavior

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <twftesla-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:
> 
> Original poster: "Alexander Rice by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <ajjrice-at-yahoo-dot-com>
> 
> 21/12/2001 15:03:59, "Tesla list" <tesla-at-pupman-dot-com> wrote:
> 
> hello malcom,
> 
> interestingly i have observed the same type of pre- breakout phenomena with
> my large
> wimshurst machine, if i open the gap to a bit longer than it can jump with
> two leyden jar
> capacitors, charge it up and then touch one terminal i can see a globe of
> beautiful
> feathery 'sparks' that extend for around 6 - 7 inches around the other
> terminal, i have no
> idea how this occurs, i can only presume by suddenly grounding one side of
> the device
> the other winds up at a huge potential relative to ground, it is really
> wierd being a dc
> phenomena as well as an ac one - maybee same effec, different reason. i
> would be very
> interested if anyone could proffer an explaination

The Leyden jars keep the voltage between the terminals constant for some
time when you ground one of the terminals. This causes a sudden doubling
of the voltage relative to ground, and surrounding air, at the free
terminal, causing the breakout. The "plume" appears clearly at the
positive
terminal. If the negative terminal is the free one, you just see some
light at the terminal surface. Exactly what is the plume is not very
clear.
I think that the many thin channels converging to the "stem" of the
plume are similar to negative leaders in a lightning spark, while the
stem is caused by sudden breakdown of the remaining space when
sufficient
charge accumulation close to the terminal occurs. Maybe the order of
events
is the opposite. Why the thin channels converge to a point somewhat away 
from the terminal instead of directly to it I don't know. If you look
closely to sparks produced by the machine in the dark, weakened sparks
are better for this (interconnect the Leyden jars through a piece of
wood), you see that the plume always appears at the positive terminal,
and that the main spark follows the stem of the plume and one of the
thin
channels. Look at this picture:
http://www.coe.ufrj.br/~acmq/tri14cm.jpg
You can see the stem as the straight segment at the left terminal.

Antonio Carlos M. de Queiroz