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interesting secondary phenomonea

Original poster: Neal Namowicz <mr_neal@xxxxxxxxxxxx>

Thanks DC,
That's basically what I meant, you just have a much more eloquent way of
putting it! Re: the St. Elmo's Fire- never saw it, but I certainly felt it!! On a similar theme- got zapped last week by a metal halide ballast that had a high
resistance short to the housing. Note to self: turn off power before changing


> Original poster: "resonance" <resonance@xxxxxxxxxxxx>
> Neal:
> It's because the charge is not residing in the metal wire which is
> connected to ground --- the charge is residing in the dielectric (wire
> coating) between the grounded wires.
> A coil does have a DC component which can momemtarily charge the
> dielectric, ie, plastic or enamel wire covering.  The def of a cap is two
> plates separated by a dielectric.
> Recall the old physics trick of the removable dielectric Leyden jar?  A
> Leyden jar type cap is charged, and, then, while charged, with a plastic
> stick, the center conductor is carefully removed and the outer conductor
> is removed.  They are shorted together, and also both shorted to a ground.
> The cap is then reassembled and the cap is powerfully discharged!!  It
> proves the dielectric stores the charge, not the plates.  In a Tesla coil,
> under certain conditions, the plastic PVC coating on the wire, or enamel
> coating, or protective coating over the windings, will hold a DC charge
> that discharges to you when you touch the sec coil.  Good idea to at least
> slowly run the back of your hand or a ground along the sec winding to
> discharge any of this "static electricity" that remains.
> Many coils usually don't have this problem some but coils with a heavy
> coating or PVC insulated wire coils can exhibit this phenomonea under
> certain conditions.  Caution is in order until you discover if your
> particular coil design exhibits this interesting process.
> The atomic electron orbitals are stretched when the cap is charged, and as
> they return to their normal obits, they give up some electric charge to
> the plates again.
> I've noted it also seems to be more prominent in coils that are suddenly
> shut off at high power as opposed to operation in which the variac is
> slowly diminished.  Perhaps a gradual shutdown of your particular coil
> will prevent this event from occuring.  You could do some experiments with
> a grounded wire in a very dark room and you may see some "St. Elmo's fire"
> as you drag the wire down the side of the secondary coil.
> Dr. Resonance
>>I've gotten bit by a couple secondaries in the past, which I thought was
>>rather odd since they were still connected to ground at the time. I'm
>>thinking that perhaps it's an electrostatic charge built up on the
>>outside of the secondary that carries the "bite". (?) Now, before I decide
>>touch a secondary that's just been running, I take a grounded wire and go
>>over the outside of it a bit. (I bend the end over so I'm not scraping the
>>finish off) Seems to have done the trick for me.

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