Electronics Forum / Basics / August 2006

*HIGHLY* doutful, I'd say.

Water in its *PURE* state is a nearly perfect insulator. SO the IDEA is
good. In practice, though...

Water with even a little contamination is anywhere from a medium-poor
conductor to better than a copper wire as a conductor, depending on the
type and quantity of contaminant.

Water-dielectric capacitors have been tried - and found wanting - by the
tesla coil types. They work great - ONCE. Generally, by the time the
second shot is ready to happen, the water has already been contaminated
enough by the metal plates leaching into it that it's worthless (or at
least lousy) as a capacitor, and the coil doesn't fire worth diddly.

On the other hand, there is the so-called "6-pack" capacitor - 6
long-neck bottles from your favorite brand of beer that comes in
straight-sided bottles. Wrap each one in tinfoil, as smooth and
wrinkle-free as humanly possible. Set them all on another sheet of
tinfoil, so that all of them are electrically connected. Now fill them
all with a saturated NaCl solution (AKA "Brine"), topped with an inch or
two of U.S.P Mineral Oil, then corked (usually with rubber stoppers).
Connect wires to 6 large nails, and drive the nails through the rubber
stoppers/corks, through the oil, and into contact with the brine. Run
the 6 wires together to a terminal. The other terminal is the sheet of
tinfoil the bottles are sitting on. Presto - One fairly large value
capacitor suitable for the high-voltage work involved with running a
Tesla coil - The tinfoil on the outside is one plate, the brine on the
inside is the other plate, the glass of the bottle is the dielectric.

I think the term for this sort of material is artificial dielectric.
A Google search will turn up lots of hits.

Sounds doubtful.  Energy is stored in the molecule/atoms of the
dielectric - they deform physically under an electrostatic field.  -
the reason why some dielectrics are good at some frequencies and lossy
at others (dissipation factor changes with frequency)  A conductor
introduced into the dielectric material might work - but because it
may serve to bring the plates closer together- effectively speaking -
and decrease the insulating ability of the dielectric - so it might
have to be thicker.  zero gain

I'd wondered about just using an insulated metal plate as the
dialectric.  But I analyzed it as two capacitors in series, and didn't
get the result I'd hoped for.

Pure water is also I think diamagnetic. What about deionized water?

Like a ferrite core? Ferrite is too hard to make.

An auto repair shop with a brake drum/disk grinder is a
good place to pick up some free iron filings. They could
be embedded in epoxy or fiberglass resion but it would not
be anywhere the same as ferrite.

What kind of voltages are you thinking about?
Some dilectrics work well only for certain voltage ranges.

What about trying some 'metal' cassette tape?

It's hard to control the property of liquid suspensions when
temperature is always moving things around. Try suspending
iron filings in gelatine or ...

Faraday wasn't recognized much for his academics.
If you want an exciting read, try his Experimental Researches
in Electricity. It gave me a great respect and inspiration for
actual experimentation. Then read Maxwell. There's an order
to the universe.

I think your physics book has over simplified it. I don't belive that it is
a simple matter of "negating the voltage across the plates" but a case of
the distorion created in polar molecules by the electric field. That
distortion is a form of energy storage and has the effect of increasing the
capacitance which shows as high dielectric constant. Negating the voltage
implies some sort of conductor within the dialectric which is what you are
asking. But that's not the phenomenon so I doubt it would be successful.
Bob

It'd work, but would it help. the particles would reduce the effective
thickness of the dielectric and that'd reduce the breakdown voltage.

If the particles are mobile they could move by electrostatic attraction to
short-circuit the capacitor.

This is the sort of thing you can play with in an electrostatics lab.

Bye.
  Jasen