At 10:17 PM 7/3/2012, Jeff Driscoll wrote:
Here are my two cents from reading up on dielectrics:
With the 6000 V capacitor isolated from the electrolyte by the
plastic, the electrolyte acts as a dielectric which reduces the E
field in the electrolyte almost to zero in the middle but increases
the the capacitance of the capacitor.
Arrggh.
A "dielectric" is an insulator. The electrolyte is not an insulator.
This system is like two capacitors with a common plate. The two
dielectrics are the two cell walls. The common plate is the
electrolyte in the cell. There are then two outer metal plates.
If there is zero ionic current then I assume there has to be zero E
field in the center of the electrolyte.
There is significant ionic current from the electrolytic current
generated by the cell power supply. There is very little current
through the cell walls.
There is not "zero ionic current." There are two currents here, the
electrolytic current from the normal operation of the electrolytic
cell, it's on the order of 1 mA maybe up to 500 mA. There is a
current in addition to this, from the high voltage supply, based on
the leakage through the acrylic, I estimated at about 0.5 nA. That is
less than a million times smaller. Undetectable under the
experimental conditions.
As soon as the 6000 V is
applied, there is a momentary current in the electrolyte and a
polarization of the dielectric electrolyte. After that there is zero
current assuming the plastic is an infinite insulator.
That is correct. This is why I mentioned DC. When the voltage
changes, current will flow until the dielectric becomes polarized.
Basically, current will appear to flow through a capacitor until the
capacitor is charged. What is happening is that charge is building up
on the plates. There need not be any actual current flowing *through*
the capacitor, but the effect is as if there were.
So the positive ends of the water molecules are facing the negative
plate of the capacitor and the negative ends of the water molecules
are facing the positive plate of the capacitor.
This has confused the electrolyte with the dielectric, i.e., the plastic.
Immediately next to the acrylic, there would be some level of
polarization of the water. But the field strength within the water
would only be tiny, far less than full polarization would represent.
The water, in this cell, is essentially at ground potential.
And that's interesting in itself. Is the HV supply isolated,
floating, or is it 6 KV with respect to ground? If the latter, then
there is no voltage across one cell wall, and 6 KV across the other.
It really doesn't make any difference. There is no discernable
electric field inside the cell, within the electrolyte, from the
external high-voltage field.
Maybe it's homeopathic.
