Re: Isotropic Capacity

To: tesla-at-poodle.pupman-dot-com
Subject: Re: Isotropic Capacity
From: Tesla List <tesla-at-stic-dot-net>
Date: Tue, 27 May 1997 23:44:19 -0500
Approved: tesla-at-stic-dot-net
Subject:  Re: Isotropic Capacity
  Date:   Tue, 27 May 1997 09:29:10 -0500
  From:   David Huffman <huffman-at-FNAL.GOV>
    To:   Tesla List <tesla-at-pupman-dot-com>


> Subject:  Re: Isotropic Capacity
>   Date:  Mon, 26 May 1997 13:47:40 -0400 (EDT)
>   From:  richard hull <rhull-at-richmond.infi-dot-net>
>     To:  Tesla List <tesla-at-pupman-dot-com>
> 
> 
> snip
> 
> >  A coiler would be interested in the exact capacitance value of
the
> >toroid
> >when on the top of the secondary coil because with the secondary
coil
> >inductance it determines the operating frequency of the TC. 
> >
> >The capacitance of the sphere is higher when isolated in space
than when
> >on
> >the TC secondary coil. Do any coilers know why?
> >
> >  John Couture
> >
> >
> I have always found that any isolated capacitance when considered
as a
> capacitive device and connected to or near enough to another
capacitive
> isolated device forms a simple series capacitive circuit.( with
> reference to
> gorund)  This makes the large device appear to possess less than
its
> full
> isotropic capacitance with reference to ground, which is where we
always
> reference most isolated isotropic capacitive measurements on earth.

> 
Now I'm really confused. As a sphere is moved away from ground its
capacitance goes up? As a second sphere is brought closer to one
being measured, the capacitance goes down? Even a series circuit to
the second capacitor is in parallel with the first wrt ground.
Am I reading this wrong? This must be one of those cases where the
real world teaches us something.
Dave puzzled Huffman


>  These series circuits are subtle and complex in multibody problems
> especially when close to the earth with relation to the sizes of
the
> bodies
> under study.  This is why the theoretical equations are just no
good for
> the
> realized values of "inuse" isolated capacities for Tesla coils.
(Always
> give
> results which are too high compared to values derived from
measurment.)
> 
> The largest capacitance possible on earth for any isolated
conductive
> body
> can only be reached when 10X its major axis from the earth. 
Otherwise
> it
> would be required to be at "capacitor plate" distances (<<<10 x
major
> axis)
> from ground to rise above that value.
> 
> Richard Hull, TCBOR
>