Re: single shot

Ed Harris writes.....
>     I have been thinking about the formation and maintainance of arcs 
> from telsa coils. Do the long secondary arcs that I see from various people 
> form in one ring-down time from the secondary, or are they formed from 
> multiple ring-downs? 
Multiple in my experience. Turns out the sparks go far farther with
repetitive ionization from multiple shots than the theoretical
voltage would suggest. Hence I regard spark length as a non-starter
for indicating actual output voltage.

>     Has anyone ever done single-shot discharge experiments 
> where the secondary is only allowed to ring-down once?

Yes, many times. The result is a spray of feathers as the secondary
rings down. Some are often a bit thicker than others showing some
of the effects mentioned above. Tesla speculates in his early work
that each feather represents a cycle of oscillation.

>     Also, I know that the resistance  of an arc goes down with 
> increasing current. So the voltage of the secondary should drop 
> considerably after the arc forms. It would be intersting to get relative 
> voltage readings pre and post arc. A scope probe placed far enough away in 
> a non arcing direction might allow one to see this effect. 
Done it, and yes. The better the spark, the quicker the oscillation
dies. With a discharge rod positioned close enough to the terminal,
the "feathers" disappear as the current flashes back and forth in
a single discharge channel.
    Loose pri-sec coupling means that the system cannot behave like
a voltage source. IMO Vo must drop with loading.