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Re: Capacitance of a long thin rod (e.g. a spark) (fwd)
---------- Forwarded message ----------
Date: Fri, 17 Jul 1998 10:24:35 -0700
From: Jim Lux <James.P.Lux-at-jpl.nasa.gov>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Capacitance of a long thin rod (e.g. a spark) (fwd)
Tesla List wrote:
>
> ---------- Forwarded message ----------
> Date: Fri, 17 Jul 1998 07:29:19 +0000
> From: "John H. Couture" <couturejh-at-worldnet.att-dot-net>
> To: Tesla List <tesla-at-pupman-dot-com>
> Subject: Re: Capacitance of a long thin rod (e.g. a spark) (fwd)
>
> Jim -
>
> If the capacitance of the TC secondary is changed by the streamers
> wouldn't this put the system out of tune and stop the streamers?
>
> Richard Hull said it was an extreme change implying much more than 5%. He
> did not say how he measured the frequencies with and without streamers under
> high voltage operating conditions.
Sure it would pull it out of tune. I suspect this is why you tap out a
bit from the low voltage resonance. That would account for the reduced
resonance. The coil doesn't need to be in as much tune to get the
streamer started, and then as the capacity increases, the behavior
changes...
Just as a ballpark guesstimate, say you had 14 turns to get resonance
w/o streamer and you need to go to 15 turns to get resonance with the
streamer. In general inductance goes as N^2, and frequency goes as
sqrt(1/LC), so the change in frequency will be the same as the change in
turns, or 7% in my example, same ballpark, so it is consistent.
I think that more precision in this sort of analysis would be spurious,
unless you went to a lot of trouble to look at the dynamic behavior of
the C.