Wire length,resonance, and Q

From:  Greg Leyh [SMTP:lod-at-pacbell-dot-net]
Sent:  Saturday, May 30, 1998 8:36 AM
To:  Tesla List
Subject:  Re: Wire length,resonance, and Q

Tesla List wrote:

> >Although there is a current node at the base (max I, min V),
> >the top winding carries both the maximum voltage _and_ nearly
> >the maximum current, just like in a standard HV transformer.
> >-GL
> My tests show that the all the current isn't making it to the top electrode.
> I think the self-capacitance is storing energy and thus "stealing" some of
> the current before it gets that high.

I think that this will depend heavily on the size of the secondary
and vary considerably from coil to coil.

A big topload will shield the self-capacitance of the secondary to a
and draw more current from the top winding as well.  A secondary with no
top electrode will have very little current at the top, just enough to
service the electric field lines coming off the top edge of the coil.

>         My recent paper describes a current test I did on my research coil.
> I found that the current going into the top electrode was about 60% of the
> current at the base (no breakout).  I found that this almost exactly matched
> the ratio of top to self-capacitance in my system.  Do you (or any one else)
> have any similar results that might add to this?

I was surprised at just how much current was present at the top winding
of my new coil -- it was within 10% of the base current!  I checked both
by placing them on the same base winding lead, and they agree to within
width of the scope trace.  I am going to duplicate the measurement on my
old coil, using a small and a large top electrode.