RE: Terry's Test - Two Manifestations of Charge

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Malcolm Watts" <m.j.watts@xxxxxxxxxxxx>

Hi Dave,

On 7 Jul 2005, at 11:01, Tesla list wrote:

> Original poster: "David Thomson" <dwt@xxxxxxxxxxxx>
>
> Hi Antonio,
>
>  > The setup: http://www.coe.ufrj.br/~acmq/tesla/2sparks4.jpg
>  > Running: http://www.coe.ufrj.br/~acmq/tesla/2sparks2.jpg
>  > Sparks and light in the tube:
>  > http://www.coe.ufrj.br/~acmq/tesla/2sparks3.jpg
>  > Detail: http://www.coe.ufrj.br/~acmq/tesla/2sparks1.jpg
>  > The average current is about 50 uA.
>
> That's a really neat setup.
>
>  > I tried to reproduce the same experiment using an
>  > electrostatic machine. It worked. And the explanation is
> trivial.
>  > I placed a fluorescent tube over a metal plate (30x30 cm),
>  > over an insulating support, and placed the two pins at one
>  > end of the tube close to the two terminals of the machine.
>  > When the machine operates, a continuous stream of sparks
>  > flows between the two terminals and the two pins. Both
>  > identical due to the symmetry.
>  > If I connect one of the terminals to the metal plate in
>  > contact with the tube, the tube starts to glow and the sparks
>  > at that side are clearly more intense.
>  > The reason is simple: The tube over the plate is acting as a
>  > capacitor, charged by the weak sparks. It discharges
>  > periodically with an intense spark between the other pin and
>  > the terminal connected to the plate, that is the outer plate
>  > of the capacitor.
>  > (I observed that I can obtain a more intense effect if I made
>  > the connection between the metal plate and the machine
>  > terminal through a Leyden jar. The jar gets charged through
>  > the leakage across the surface of the glass tube, and the
>  > sparks are longer.)
>
> This is very interesting.  The tube and plate are acting like a
> capacitor.  That makes sense.  But wouldn't the capacitor act as
> a transformer and reduce the potential in order to increase the
> current?  In other words, the thinner spark would be higher
> potential, lower current.  The thicker and brighter spark would
> be lower potential, higher current.  The total power in each
> spark would be the same, correct?
>
> Dave

All that I have learned through experimentation and measurement says
a loud "no" to your last question. Spark brightness is dependent on
current and spark channel resistance drops in a non-linear fashion as
current increases which means you cannot treat power in a spark
channel as you would in a (for want of a better term) linear
resistance. The strike distance is a function of voltage in the
situation you are looking at. If the distances for the two sparks are
the same and one spark is brighter than the other, which would you
say is dissipating the most power?

Malcolm