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Re: pure water capacitor?
Hi,
>I've been trying to do some research regarding design issues, when I came
>across a list of dielectrics for some materials for use in capacitors. The
>dielectric constant for pure water is around 85 with an infinite breakdown
>voltage!
It sounds wonderful... but...
Bad thing is you'll never get even close to "pure" dielectric water -
first of all the autoprotolysis (OH- and H3O+ from 2*H20) will make the
water always slightly conductive no matter what, then also the two
(insulated or not) electrodes placed in the water will make the cap a
lovely electrolysis and/or O2 and H2 generation chamber that will explode
right in your hands if there's any chance of corona forming around one
electrode and igniting the highly explosive H2+O2 gas mixture. :o(
If current is low, 30mA or so, then maybe you could use some method of
pumping out the gases and feed in new water...
But, the water cap won't work, because the polarized molecules are free to
flow from one electrode to the other along the electric field. They don't
remain in place like they should.
Not to mention impurities that come either from the electrodes themselves,
or the container material, or the surrounding air leaking in. The
impurities alter the dielectric and conducting properties of the water.
Only thing that you could try to do is a ice capacitor - distill water and
freeze it in a vacuum, then use the ice as dielectric. Moving molecules
shouldn't be a problem then, neither water conduction, nor gas generation.
But you'd have to keep the thing cooled down somehow, and try to ban all
corona around the electrodes. :(
Just a thought.
--
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Jan Florian Wagner