Re: Sparks - Bright in the middle, how to verify it.

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

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

Tesla list wrote:
> 
> Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<Tesla729-at-cs-dot-com>

> One thing that I have noticed that I'm sure a lot of others on the
> list have recognized is the "bright on one end" phenomenon with
> HVDC discharges. This is noticable with Van de Graf generators
> and other such HV pulsed DC sources. It is my understanding
> that  the brighter end is the positive terminal and consequently,
> the dimmer end is negative.

Short DC sparks taken from a low-capacitance source as a VDG generator
are really brighter at the positive end. There is a distinct bright
segment at the positive side, followed by a dim and diffuse segment
going to the negative side. As the energy (and the length) of the spark
increases things get more imprecise. Bright or dim segments appear at
other points (standing waves?). Higher energy sparks (discharges of
Leyden jar capacitors, for example) can look brighter at the negative
side instead, but not only in a short segment. Look at these, brighter
in the center, from a Wimshurst machine with 2.15 meters disks:
http://www.coe.ufrj.br/~acmq/rovc6.jpg 
or this spark (14 cm) from a smaller machine, brighter at the
negative end:
http://www.coe.ufrj.br/~acmq/tri14cm.jpg

Antonio Carlos M. de Queiroz