Re: [TCML] Spark gap comparisons

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In a message dated 2/23/2008 9:28:00 P.M. US Eastern Standard Time,
bartb@xxxxxxxxxxxxxxxx writes:

> You said that the wide (5/8") gap in my triggered gap would   not
> result in higher gap losses compared to the shorter gaps in  the  rotary.
>
>I said I don't understand how it  could. Why would a "longer arc" have a
>higher resistance unless it is  viewed as a piece of wire? This is the
>first step. If we look at the  longer arc as a wire, the longer the wire,
>the higher it's resistance.  I understand that hands down. But an arc is
>not a piece of wire. The  arc is a variable where the resistance goes to
>near zero from it's  initial infinite state (of which is where we attain
>the negative  resistance appearance, not real, but appears to be) as a
>function of  the change in current. In a piece of wire, it is a steady
>state  resistance and very easy to account for.

Hi Bart,

My thinking was that for a given coil, increasing the arc length
would tend to increase the arc resistance, since mostly everything
else is staying mostly the same; the bang size, the peak  currents,
the bps, the spark streamer output lengths, the winding  resistances,
etc.  I would think that if these things were shifted rather  radically,
then the arc resistance would shift radically, but if these things
are pretty much constant, then the arc resistance should be
somewhat "agreeable".  The type of materials of the gap can
have an effect, but I think it tends
to be a small effect.  I would think the change in losses (due  to
arc length) would have the largest effect.  I just don't see  why
making the arc much longer would be expected to have no effect
(on arc resistance),
in a situation where mostly everything else in the coil is mostly
the same.  But you may be right.  I'm not an expert on  gap
physics.  Yes, more experiments and research is needed.
What's interesting to is that many of these experiments are
not really difficult to perform, so I'm surprised that more folks
have not done them.  Just looking at peak voltages, peak
currents, ring down decrement, quenching, etc. would tell
a lot, when comparing gap systems.  This work can be done
on a small table top system, so that the sparks won't be
hitting walls and generally creating havoc during the testing.

John

>An arcs resistance is quite different and variable to the  current
>without a definitive value. This arc resistance can match  whatever is
>thrown at it (from an 1/8" to 1" without a measurable  difference [well,
>unless some seriously acquisition is  used]).

>I think we view an arcs length as a length of wire and this  is the
>problem. An arc is not a length of wire. In the end, we can of  course
>average the resistance accounted "as" a length of wire. The  gaps you ran
>should have differed quite a bit if arc resistances were  similar to a
>length of wire. If the resistance was "not" definitive  (and I don't
>believe they are), then it is very possible the arc  resistance is the
>same or very near so for a long length and a short  length (and time
>defines their realized energy). This is an area that  we just haven't
>really explored in detail yet. Your experiments I  think are the closest
>that anyone has attempted, and those experiments  state the arc
>resistance is something to be further experimented  with.

>I "cringe" at what I've read at times mainly due to realizing  the
>inputs. I don't know any of this for certain. I am simply trying  to
>figure out what is real and what is not. The spark gap is one of  the
>most incredible and worthy analysis of any mechanical system I  know of.
>It rivals even resonant coil physics, and oddly, so closely  related.

>Take care,
>Bart

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