XPost: sci.physics, sci.electronics

On Sat, 31 Jul 2004 23:23:31 GMT, Mark Thorson <nospam@sonic.net>
wrote:

Quoting from INDUCTION COILS HOW TO MAKE AND USE THEM
by Marshall and Stoye (Spon & Chamberlin, 1906),
pages 65-66:

"For ordinary sparking experiments the negative electrode should
terminate in a fairly large brass disc, the positive being a needle
point adjustable as to distance, but moving opposite the centre
of the disc. By this means the longest sparks can be obtained.
It will be noticed that the sparks constantly strike fresh places,
and they almost invariably traverse very crooked paths through
the air. In this respect they are like lightning flashes -- 'small
editions' of which they really are, as a matter of fact. These
crooked paths represent 'lines of least resistance,' the electric
current, no doubt, finding irregularly distributed particles of
conducting matter floating in the atmosphere."

Is that really why electric arcs follow an irregular path?

Dust is not a requirement for a crooked path. The first spark's path
could follow locally high concentrations of air. The spark produces
high conductivity remnants that can move during the time between
sparks. As the concentration of conductive material increases, spark
length can increase.

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