Re: Charge stored in Dielectric? Not really - MISCONCEPTION

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Antonio Carlos M. de Queiroz" <acmq-at-compuland-dot-com.br> 

Tesla list wrote:

 > Original poster: "Luke" <Bluu-at-cox-dot-net>

 > Forget about the oil and trying to prevent that corona from leaking onto
 > the dielectric.  Why wouldn't it work at 500 volts if the charge was on
 > the dielectric?

This depends on how the capacitor is built. Two loose plates and a
dielectric plate leave a lot of air between the metal plates and
the dielectric. The voltage is not high enough to cause sparking
through the air separating the plates from the dielectric, and most
of the charge remains in the plates.

To complicate:

Consider another classic experiment, the "electrophorus".
http://www.coe.ufrj.br/~acmq/eletroforo.jpg
On it, a metal plate is placed above a charged dielectric plate with a
grounded conductive back plate and touched (grounded).
When the plate is touched, a spark occurs.
This is equivalent to the reassembly of the dissectable capacitor,
where the reassembled capacitor becomes charged with the same
original polarity. The spark "discharges" the reassembled capacitor.
Or not?
It's well known that the touched plate becomes charged with
the -opposite- polarity of the charged surface, and that the
dielectric plate doesn't lose much of its charge when the
electrophorus is "assembled" (The main use of the device is to
generate charge at high voltage in this way).
This happens because in the assembled position the electric fields
are low, insufficient to force charge movement between the areas
of the dielectric plate that don't directly touch the metal plate
and the metal plate.

Note that to observe the opposite charge in the plate of the
electrophorus, it must be removed from the dielectric plate
"straight up", and the plate must have rounded edges. If it is
moved sideways and has sharp edges, we repeat the "disassembly"
of the dissectable capacitor in a variant way, and the charges
in the plate spark to the dielectric plate, cancelling the
charges there, with a discharged system resulting.

It's possible to make a large number of curious experiments with
an electrophorus. Look at the picture and see if you can deduce
what is being done.

Antonio Carlos M. de Queiroz