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supercaps



       On February 22  Leigh Palmer wrote
> I'm unsure of what is meant by "chemical energy" in this or any other
> context. This phrase, like "heat energy" is a trap. Energy is energy.

Yes, a lot of interesting depth is hidden behind each form of energy.
Chemical energy does have an accepted meaning; it is potential energy
of forming molecules (from atoms or from other molecules). As far as I
know, no chemical energy is involved in charging and discharging of a 
Leyden jar. Yes, work done to polarize molecules of glass goes into
potential energy but I would not call it chemical energy (unless you
convince me that SiO2 changes into something else). 

I would infer, from your description of the rebounding of voltage in 
glass, that polarizational potential energy does not dissipate entirely 
when the Leyden jar electrodes are connected for a short time.

      Leigh also wrote:
> If the behaviour of the supercap on rebounding after discharge is taken
> to represent this arcane sort of energy, then it must mean equally that 
> a capacitor with a glass dielectric stores chemical energy, too. ... 
> Kinescopes are capacitors. They are effectively Leiden jars. ....
> The rebound phenomenon with a glass dielectric capacitor is quite
> dramatic. You can demonstrate it with a Leiden jar as well. In fact I 
> do it with a disassemblable Leiden jar. I can charge the jar and remove 
> the aluminum electrodes. After touching them together, I replace them and 
> a healthy arc can be drawn off the jar. After a minute or so I can draw 
> another spark.

Very interesting; I did not know about multiple sparks in jars. What does 
the removal of electrodes have to do with the showing of these sparks? 

> The capacitance of an electrolytic is simply the parameter Ludwik
> measured in his experiment. No electrolytic, supercap or otherwise,
> behaves linearly.

How do manufacturers determine C; from the discharge rate or from the
defining equation, Q=C*V? For your Leyden jar both of these approaches 
are likely to yield practically the same C. I found the same to be true 
for the non-electorolytic and for the "ordinary" electrolytic capacitors 
(C<2200 microfarads) which were tested. Supercaps seem to be unique in 
that respect.
                                                         Ludwik Kowalski