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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:  Wednesday, February 11, 1998 6:00 AM
To:  Tesla List
Subject:  Re: 0.5*C*V*V vaild?  (Was Output Voltages and Voltage/Length)

Mark S. Rzeszotarski wrote:

> >I have also noticed in PSPICE that the voltage dist
> >along the sec becomes much more linear when a large
> >topload is added.
> >If the voltage dist along the sec is mostly linear,
> >then is it reasonable to treat the sec ckt as lumped
> >elements, and forget the 'antenna theory' treatment?
> >-GL
>         Regrettably, I think the answer is yes.  The math is really
> interesting but in the long run the system sure acts like a lumped circuit.
> The voltage rise along the secondary is nearly a sine wave from 0 to 90
> degrees along the length of the wire if no toroid is added (typical tube
> coil).  With a large toroid on top, the phase angle may only go through 0 -
> 60 degrees or less, and the voltage distribution is much more uniform, since
> sine(theta) is approximately linear for small theta.  There is also an
> electrostatic shield effect brought on by the toroid which helps prevent
> breakout from the turns near the top, where potentials are several orders of
> magnitude greater than the breakdown voltage of the insulation.
>         

Also in PSPICE I've noticed that when the sec doesn't
have a topload, then the voltage dist _looks_ like a
quarter-sine, but doesn't actually _map_ onto one.
The curve more readily maps onto a y=SQRT(x) function.

Perhaps the non-linear voltage dist observed on TC's is 
not a sine at all, but an exponential curve, having more 
to do with the primary field dropping off with distance.


-GL