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Re: Capacitors.........
>Original Poster: "James" <elgersmad-at-email.msn-dot-com>
>
> Well, I already know about the internal construction, and they look like
>a can, filled with carbon. Somewhere after the dielectric isolation, there
>is a layer of tantalum foil. It is really looking like solid carbon's
>reaction to tantalum. It is that strange, and I was wondering, if anyone
>has done any measurements, because Nikola Tesla did. He measured the
>capacitance of the Earth in respect to, a what I don't know, but his
>determination was that the Earth's capacitance was at .1 uF or .01uF if I
>don't remember rightly. So, if tantlum is way up there just because of it's
>chemical response to carbon, is there another metal that can do similar?
The choice of metals in the construction of a capacitor makes no
difference, it's just the geometry of the plate conductor that matters.
The reason tantalum is used is that it can be formed as a sponge-like
mass of particles with a very high surface area per volume. An oxide
layer is then grown over this sponge, and it is this oxide layer that is
the dielectric. Again there's nothing magical about this oxide layer, it
just has a very high surface area to volume ratio. In any event, the
oxide layer's maximum voltage is very limited in tantalum caps, is valid
only for DC applications, and these are TOTALLY WORTHLESS in a Tesla coil.
See http://www.avxcorp-dot-com/tech/tantalum.htm for a very detailed
explanation of tantalum capacitor construction.
>I was once doing experiments with charging a 30 ft long piece of wire,
>and I place some foil onto my tv screen before it warmed up. Then I let
>it warm up, when I hung a weight from the middle of the 30 ft piece of
>wire strung with a little slack between two tacks. It contracted when I
>shorted it to earth ground as though the electrons were just occupying
>space. So, there must be a static value for any given element on the
>table of elements, and I was wondering if there was a way to measure
>that. Between earth ground, and the block of metal itself being isolated
>from earth ground?
What you did was to create a capacitor using your foil as one plate, the
CRT glass as the dielectric, and the CRT's anode as the other plate. You
charged up the foil plate, not the wire.
By "static value", I assume you must mean dielectric constant. This is a
property only of insulators when forming the dielectric layer between two
conductive plates, and in your case, the CRT glass face. The choice of
insulator will affect the capacitance. The choice of conductive plate
material has NO effect on capacitance, assuming plate geometry stays the
same. Tables of dielectric constants for all reasonable capacitor
dielectrics have appeared recently on this list and are in the archives,
no need for anyone to measure them again.
>I guess I'll have to do something pretty soon. Possibly with a roll of
>quaters, because they're all the same size, and I can get allot of em'.
You mean use quarters for plates in a capacitor? Why do you want to use
something so small and expensive?
Gary Lau
Waltham, MA USA