Re: Lightning vs. Tesla Coil Discharges

On Mon, 08 Nov 1999 06:20:17 -0700 Tesla List <tesla-at-pupman-dot-com> writes:
> Original Poster: "Reinhard Walter Buchner" <rw.buchner-at-verbund-dot-net> 
> Hi All,
> While reading Jim Lux´s answer to my post on filming
> TC arcs, a few questions popped into my head:
> While coils can be (and ARE) very impressive, I´m sure
> all will agree lightning is the hands down winner, when it
> comes to the *really* impressive discharges.
> What is a cloud in the sense of source? Is it *just* an
> ultra high voltage source or is it a high current source? I
> would guess the latter, because the plasma channels
> lightning creates can easily be several inches (maybe
> even feet) in width. This discharge channel gets so hot
> that we can hear the air being displaced (the thunder).
> Wouldn´t a Marx generator be a more *exact* equivalent
> of man-made lightning?

I think I read somewhere that lightning is somewhere in the 10^9 order of
magnitude.  I definetely agree with this.

> What capacitance (roughly of course) does a cloud have?

That isn't difficult to calculate.  We all know the dielectric constant
of air is one, so if anybody knows average cloud height and area we have
our answer.

> >Current keeps flowing because once the channel is
> >formed, it's resistance drops dramatically (that
> >negative V/I curve).
> This might well be the reason why a TC will almost always
> perform better with a larger toroid. The more Ctop, the
> more current (and not voltage) our TC can deliver to the
> arc channel. Maybe it is also the reason, why low voltage
> (high current) powered coils don´t perform worse than
> hv coils do ;o)).

I believe that this is also a function of more efficient energy transfer
with higher current but I am not a HV engineer.  Does the v/i curve mean
that higher capacitance (to a point of course)will give you higher
voltage output because you can maintain the spark as its voltage drops in
a marx generator?

> >Once the channel has reached 7000K, the conductivity
> >is so high that the IR heating drops off.. Essentially, the
> >entire leader is "regulated" by a sort of negative feedback
> >(heat loss proportional to T^4, heat input proportional to
> >I^2R, which is inversely proportional to temperature) to a
> >temperature just high enough to keep it "well ionized". So
> >the point where two leaders meet is probably no hotter
> >than anywhere else along the leader.
> This brings another thought to mind. What would happen
> if we could (in some way) make a discharge path which
> is surrounded by a gigantic magnetic field? This should
> keep the plasma bundled and very hot. What would happen
> if we constructed this magnetic field similar to a coil gun? In
> other words using not one, but several magnetic coils along
> the discharge path. Could one accelerate or even stretch
> the actual coil discharge?

I don't think so because magnetic fields make electrons spiral(this is
why an uwave has such fat magnets) which increases breakdown voltage. 
Alas, I am no HV engineer and I could not tell u for sure.
> Coiler greets from Germany,
> Reinhard
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