EVP wrote:
<div class="moz-text-flowed" style="font-family: -moz-fixed"> I
should know the answer to this but I don't and hope someone here can
help.. What is the polarity of the two ends of a DC spark when one
is purplish and the other bright blue or white? I'm sure it's been
covered many times but can't remember the answer. Reason for
question is the color of the sparks from the spark coil I built using
GM ignition transformers. Because of the way it's excited the
secondary pulse is more or less unipolar and shows these colors
although not as strikingly as a spark from a VDG.
DC sparks, if not too strong, have the appearance of a brush, with a
short straight stem at the positive end. I have never seen a good
photo of this. When more charge is available, the spark apparently
starts in this same way, but then forms a bright spark that follows the
stem, having a straight bright segment at the positive end, and is a
bit more diffuse at the negative end, but not always less bright.
Some pictures that illustrate this:
Straight segment at the positive end:
http://www.coe.ufrj.br/~acmq/bbspark.jpg
Several sparks, clearly brighter at the positive end:
http://www.coe.ufrj.br/~acmq/trmspk.jpg
Ball-plane spark gap. Positive at the ball. It doesn't produce long
sparks if reversed:
http://www.coe.ufrj.br/~acmq/wazlspk.jpg
Antonio Carlos M. de Queiroz
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