Re: an experiment with dielectrics

Tesla List wrote:
> >From kdc4n-at-viper.cs.virginia.eduThu Jul 18 22:22:49 1996
> Date: Thu, 18 Jul 1996 12:32:23 -0400
> From: kdc4n-at-viper.cs.virginia.edu
> To: tesla-at-pupman-dot-com
> Subject: an experiment with dielectrics
> Hello all!

> means that the capacity of a standard aluminum-glass-aluminum
> sandwich capacitor should be increased by putting a small layer
> of a dielectric with a high dielectric constant between the
> aluminum plates and the glass dielectric, resulting in a sandwich
> configuration as follows:
>          ***** Aluminum plate ******
>        dielectric with a high constant
>        dielectric with a high constant
>          ***** Aluminum plate ******
> Although this increases the distance between the aluminum plates
> (lowering the capacity), the high dielectric constant in close
> proximity to the aluminum plates should more then make up the
> difference, especially if dielectrics with a high permittivity,
> such as distilled water (80), titanium dioxide (86-170), or
> manganese dioxide (~10,000) are used.  (All permittivity values
> came from the CRC handbook of physics.)
> I know that there is *some* titanium-based chemical that can be
> used to increase the capacitance of capacitors, due to the
> existence of "titanium capacitors", which exhibit large
> capacities in small packages.  What are the builders of these
> caps doing that allows them to use the high dielectric constant
> of whatever titanium chemical they are using?  (What titanium
> chemical are they using anyway?)
> Thanks in advance for any insight or explanations that you can
> give me on this matter.


I am a Tesla coiler in Richmond, Va, not too far from Va Tech.  I am a 
systems engineer for a local firm.  Your experiment is very good, but 
lacks some critical controls.  The most important control is the pressure 
and distance of the "squeeze".  Is it consistant?  I have built a number 
of caps and study this thing from both an electrodynamic and 
electrostatic perspective.  The slightest change in pressure can yield 
20% or more differentials in C when you think you have gotten everything 
you can get out of it.

I would hate to go up against a former professor, but I am actually done 
this stuff and the bulk of the dielectric, not a thin layer of paste next 
to the plates stores the bulk of the charge.  Charge is separated within 
the entire  bulk of the dielectric and this charge then "concentrates" at 
the plates!  Naturally, any dielectric of a tremendous dielectric 
constant will boost the value of the capacitance in proportion to its 
thickness and dielectric constant vs. the thickness and constant of the 
plastic sheet.  Try this more significant experiment.  Take a 60mil 
thick piece of polyethylene (3 X 3) now try your paste experiment.  I 
think you will find virtually no difference in capacitance (Within the 
limits of your abiltiy to consistently squezze the material.)  You didn't 
state the thickness of your plastic dielectric, but I bet it was rather 
thin making the paste a rather larger proportion of the dielectric than 
in my suggested experiment.

You would be amazed at how many people actually believe that the charge 
is held in or on the plates of a capacitor!  The plates are only a way to 
 apply a gradient to the dielectric and to drain it.  The charge is 
always retained 100% within the dielectric!  The plates are rather 
superfluous and not required.  They incapable of storing energy except as 
an isotropic capacitance in air or free space where these media (k=1)are 
the dielectric.

I would be glad to discuss this matter further, if you wish.

Richard Hull, Tesla Coil Builders of Richmond