RE: DC Tesla Coil - was rotary spark gap

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "David Thomson" <dwt@xxxxxxxxxxxx>

Hi Gary,

> But the variometer is essentially the primary and will pass the full
primary current, no?  Or were you using the variometer configuration
on the secondary?  I would think the end-to-end secondary voltages
would be unmanageable for a variometer.

I see what you're saying.  You're right.  I'll try to have a roll of
12 gauge flat magnet wire added to my order.  I want the variometer in
the primary circuit.  Although, I would think the 24 gauge could
handle 150 watt peak power at 30KV.  I need to look at the wire
charts.

> I also found that my oppositely wound flat spiral secondary coils
have a
 > constant potential on them of 7 to 10 millivolts.  Does your
opposite wound
 > spiral also have a constant potential on it?  I haven't measured
for a
 > current, yet.

This is a DC potential you see, with no other power applied to the
coil?

No, the potential is AC and measured with an HP 34970A DMM and
continually charted over an hour of time.

> Sounds like you have some galvanic action occurring - perhaps you
were touching the metal with your hands?

I took all the precautions of cleaning the wire ends and terminals and
supported the coil on an 18" stand away from all EM radiation.

> Or if it's AC, could something else be magnetically coupling to it?


Yes, all the ambient EMR from the room and Earth must have been
coupled to it.  It was just amazing how sensitive the opposite wound
flat spiral coils are to the slightest change in magnetic fields.
That would suggest the coil would make a great crystal radio antenna.
In fact, I need to try that.

> There's no explanation shy of perpetual motion that could cause
un-energized coils of any geometry to produce power by themselves.

I don't think that is what's happening at all.

Dave