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[Phys-L] Re: Looking for electricity demo apparatus

"... because they have very high current capability to accompany the high voltage."

don't think so.

I just measured the power consumption of two of my hand held Tesla coils *. They both are about 25 W with it's draping ~ five W. when it discharges to a conducting object. I suspect the majority of that energy is consumed by the spark gap. As a comparison, the GE XRD-5 minimum setting (one mA at ~ 10 KV) is ten W. this is for alignment. Typical operation is 40 X this and, of course, w/ considerably more efficiency. Not only because this is the energy of the electron beam not the energy into the HV transformer, but because the efficiency increases w/ HV and the Z of the target.

I wonder if his measurements were an artifact due to the RF radiation.

* These are unusual as a 2 KV transformer is separate from the coil / wand.


Karl Trappe wrote:

Before you get too carried away with the joys of the spark coils and
tesla coils, remember that stopping 10KV (?) or so against metal
usually results in x-ray production. The spark coils are especially
notorious for producing more radiation than those defective x-Ray
machines at many dentists' offices...apparently, because they have
very high current capability to accompany the high voltage.

Check with Cliff Bettis at Nebraska. He wrote an article on spark
coil radiation that's enough to scare your pants off! He was the
radiation safety officer for his department, and had to ban his own
lecture demo apparatus. I think the high frequency nature of the hand
held tesla gets around the danger. But mostly, be safe. Karl

They are either spark coils or Tesla Coils. they are often easily
repaired (I've repaired for others and myself.) Check the Chem. dept.
or other vacuum people They are (gross) leak detectors.

Did you feel a shock or a burn? The Tesla coils are rather high
frequency oscillators, so the skin effect prevents shock. If one holds
a metal object to receive the "spark" one feels nothing, but a direct
discharge to the skin results in first warmth and then a burn. If you
feel a (definite) shock then the device is a spark coil similar to one
used for the ignition in early auto's. The main obvious difference is
the spark coil has a ferromagnetic core (bundle of iron wires for dc
use), while the Tesla or Oudin coil has no core (air). You can use
spark timer (used w/ Behr free fall and other waxed tape uses, e.g.
Atwood machine and air track carts). Especially if it has a variable
frequency adjustment. (Set it at max.).. Also both Wimshurst and Van de
Graaf generators will "lite" gas tubes.

You can make your own. Tesla instructions abound on the webb and an
auto ignition coil may be driven by a distributor substitute.
(oscillator driving a switching transistor.)

BTW, that knob (button) adjusts the spark gap if a Tesla coil, or the
tension of the interrupter (exactly the same as a buzzer or electric
bell) if a spark coil.

Finally, mail them to me (contact me off list) and I'll be pleased to
attempt a repair.


p.s. if all else fails purchase one for $213 from KIMBLE glass co.

That's cheating tho.

Gonzalez-Espada, Wilson wrote:

Hello all:

Here at Tech we had two 14" handheld "sparkers" (dated 1963) that
we used for electricity demos. They were brown, with a 3" metal tip
and a variable button resistor to adjust the size of the sparks.
They produced a spark that lit a fluorescent lamp. The current was
low enough that we used it to "shock" ourselves painlessly (kind
of; it left tiny red marks that dissapear in 24 hours).

The "sparkers" are dead now. They sound as if they are working but
no sparks are produced. We need to replace them ASAP.

1. What is the correct name for this apparatus?
2. Where could I find a replacement?

I have search the Internet, but without the proper name I have been
unable to find a replacement.

Thanks in advance,

Wilson J. Gonzalez-Espada, Ph.D.
Asst Professor of Physical Science/Science Education
School of Physical and Life Sciences
Arkansas Tech University
1701 N. Boulder Ave. (McEver Hall)
Russellville, AR 72801
(479) 968-0293
(479) 964-0837 fax

Sent via the WebMail system at


Dr. Karl I. Trappe, outreach consultant Home (512) 264-1616
Research Scientist Associate V (retired)
Senior Lecturer in Physics (retired)
Physics Department, Mail Stop C-1600
The University of Texas at Austin

Austin, Texas 78712-1081

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