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Re: Capacitor with bottle, water & salt




> Original Poster: "Samuel Rosset" <samr-at-chez-dot-com> 
> 
> 
> I plan to build my own capacitor rather than buying one. I saw many
> interesting plans for caps made with bottle with a slat-water solution in
> it and that's what I'm planing to build. But I have a question: With high
> voltage in salt water, don't you have decomposition of the water in
oxygen
> and Hydrogen, which can lead to an explosion??? 

It's high frequency AC, so the ions don't really have time to move to the
electrode and collect to form the gas. By the time the ion gets moving, the
current reverses on the next half cycle and the ion gets pushed back from
whence it came.


and... How can you find to
> capacitance of such a cap... It is not as easy as with a plan or spheric
or
> cylindrical cap...

Empiricism rules the day with salt water caps. You build it, then measure
it or just try them.  A cylindrical approximation with a flat end works
nicely for a order of magnitude estimate. That's why you need to be able to
adjust the tap on the primary for tuning: you don't know what the
capacitance really is ahead of time (nor do you really know what the
resonant F of the secondary is (under load) either, for that matter)...