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Is 0.5*C*V*V vaild? (Was Output Voltages and Voltage/Length)



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From:  Greg Leyh [SMTP:lod-at-pacbell-dot-net]
Sent:  Thursday, February 05, 1998 6:58 AM
To:  Tesla List
Subject:  Re: Is 0.5*C*V*V vaild?  (Was Output Voltages and Voltage/Length)

Jim Monte wrote:

[snip]
> A Tesla secondary has distributed capacitance rather than a lumped C.
> Circuit theory indicates that ac variation is with time only, not with
> time and position.  For example, if a 60 Hz ideal current source is
> applied to several resistors in series, they will all see the maximum
> current at the same time.  This is due to the assumption that circuit
> dimensions are small relative to a wavelength.  This is not true for a
> Tesla coil.  Suppose that the maximum voltage distributes itself with
> respect to position so that only some of the total C sees most of the
> voltage.  This would seem to possibly allow a higher voltage than would
> be obtained by finding the total C and solving for Vmax based on energy
> considerations.

This is almost certainly true, especially for TC's 
with little or no topload (such as Tesla's Magnifier
at CS).  For TC's with large toploads, where Ctop is
comparable or larger than the distributed capacitance
of the coil, the E= 0.5*C*V*V equation is more accurate,
since Ctop is a lumped element, and will store most of
the energy due to the V*V term.

Even with the most optimistic projection of TC output,
where _all_ of the secondary energy is in the toroid, and
none of it is in the distributed capacitance of the coil,
many coils fall far short of their advertised output values.


-GL