Re: On sparks

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

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-uswest-dot-net>" <jimlux-at-earthlink-dot-net>


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Thursday, March 29, 2001 3:55 PM
Subject: Re: On sparks


> Original poster: "Kennan C Herrick by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <kcha1-at-juno-dot-com>
>
> >From KCH:  This just came in when I emailed my response to Bert Hickman's
> posting...so I'll just stay in the responding mode, with comments
> interspersed:
>
>
> On Thu, 29 Mar 2001 11:32:49 -0700 "Tesla list" <tesla-at-pupman-dot-com>
> writes:
> > Original poster: "Jim Lux by way of Terry Fritz
> > <twftesla-at-uswest-dot-net>" <jimlux-at-earthlink-dot-net>
> >
> > >
> > > There are some interesting energy insights here...
> > > The E-field and base current measurements imply that it takes a
> > > comparatively large amount of energy to initially form the leaders
> > versus
> > > the amount required to maintain them (at least for near CW
> > operation).
> >
> > This is pretty much to be expected... once the spark channel is
> > established,
> > the resistance of the channel drops, so you don't need as much
> > voltage to
> > keep the charge flowing fast enough to keep the leader head moving.
> > I
> > suspect that the leader head only moves on one polarity of the RF,
> > and that,
> > during the other half, the charge is flowing back down along the
> > spark
> > channel (keeping it hot).
>
> Don't know that I can agree:  Is not the spark very like a mere hot
> resistor?...in which the ac current from the coil/toroid flows back &
> forth just as it does in those components?  A hot resistor with a pointy
> end, of course, as you point out so pointedly below.

but its a resistor that changes value dramatically in the early stages of
development.  High at first, low after it's gotten good and hot.


> >
> It seems to me that that charge in a big top load doesn't do a whole lot,
> if anything, in sustaining any given length of spark.  Once the spark
> starts, that charge is history.  After that, it's what power the primary
> can continue to pump in, via the inductance of the secondary partially
> acting undesirably in series, perhaps, that's important.

The source impedance of the secondary is really high in comparison to how
fast the spark channel develops.  I think that any growth in the spark has
to come from charge stored in the top load, where it has a low inductance
path to the channel.  With everything set up right, I can see the spark
growing, and charge flowing from the secondary L into the topload and thence
into the spark on sort of a continuous basis, but I'm not sure that this
would really work.  Sparks grow pretty fast, so you're talking nanosecond
time scales for the growth, and microsecond time scales for charge to move
from L into C.

> >