Re: High Voltage Experiments

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Antonio Carlos M. de Queiroz" <acmdq@xxxxxxxxxx>

Tesla list wrote:

> Original poster: William Beaty <billb@xxxxxxxxxx>
> If TC secondaries can give DC shocks, and if it works when we rub the TC
> with cloth, etc., why doesn't this work with PCB rubbed with fur?  I took
> a piece of single-side glass/epoxy PCB, grounded the metal side, then
> rubbed the plastic side on hair.  Nuthin.  No big e-fields, no NE-2
> flickers.  Apparently the hair/epoxy pair doesn't separate much charge.

The charge is there. Try the experiment below. Maybe you need another
kind of material as rubber.

> Next, I sprayed the epoxy side with a negative ion generator needle array.
> Sure enough, when I then dragged an NE-2 across the plastic it flickered.
> So next I sprayed more negative charge on the plastic, disconnected
> ground, then lifted the board and *dropped* it onto my hand, plastic side
> down (in other words, I let go of the metal before touching the plastic.)
> My hand now supplies one capacitor plate.  Then I let the metal edge of
> the board touch my forearm.  SNAP.  Coooooool!  It's an "electrophorus"
> with human capacitor plate, just like the very first Leyden jar.

Try metalyzed plastic film.

> I'll have to try this with other materials.  Maybe a PE or teflon sheet
> with aluminum foil cemented to one side would give me painful zaps after
> rubbing it with hair.   Or use sheet metal with rubber glove stretched
> across one surface.

In the classical electrophorus, the "cake" lies over a conductive plate,
and when rubbed shows only weak charge, because most of the electric
field goes straight down from the charges on top of the plate. In the
old literature, the charges are said to be "dissimulated". With the
back plate, much more charge can be accumulated over the cake before it
starts to spark.
If the cake is rised from the back plate, the field appears clearly.
If the top plate is placed over the cake, even with the back plate below
the cake, most of the electric field points to it, and so it becomes
strongly charged. Try to use your PCB, with the metal plate grounded,
as the cake of an electrophorus.

> So why doesn't this happen all the time with beverage bottles?  If you
> accidentally rub a plastic bottle on a wool blanket or jacket, then firml
> grasp the bottle and touch the liquid to your lips, shouldn't you get a
> wallop?

This can happen if the internal liquid is grounded when you rub
the bottle. And of course, the bottle material must be highly insulating
for this.

  Maybe cold drinks always create condensation which shorts out the
> excess charge faster than fur creates it.  (So try it with warm liquid.)
> Or maybe we'd have to ground the liquid contents while rubbing the bottle
> with fur, and if the liquid is electrically floating, potentials are
> somewhat equal, so no zaps?

You are right.

Antonio Carlos M. de Queiroz