Re: Am I Right ? (fwd)

---------- Forwarded message ----------
Date: Tue, 14 Jul 1998 22:31:19 -0700
From: "Antonio Carlos M. de Queiroz" <acmq-at-compuland-dot-com.br>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Am I Right ? (fwd)

Fred wrote:

> I think I understand now what is going on inside the Tesla coil, but
> correct me if I am wrong.
> We need to achieve maximum current transfer through the primary coil
> (Tesla coil).

The "Tesla coil" is all the system. You want to transfer all the energy
in the primary capacitor to the secondary capacitor (self-capacitance
of the secondary coil + "body" capacitance of the top terminal).

 To achieve this we  need to achieve resonance between the
> primary and secondary coils. Maximum current transfer occurs only at
> resonance where the impedance is at the lowest level. With nearly zero
> resistance  to current flow, maximum field can be achieved and induced
> directly into the secondary winding.

To see how the energy transfer works, experiment with two pendulums 
with strings of the same length supporting different weigths. They 
with the same period (are in tune).
Fix a light bar from one string to the other, close to the points where
the strings are fixed, to couple the pendulums. Give a small push in
the heavier one and see what happens. With the system properly adjusted
you will see that the oscillation moves periodically from one pendulum
to the other, being wider in the lighter pendulum. A Tesla coil does the
same, where the oscillation amplitude is seen as voltage.
(I tested the idea using a toothpick for the coupling. It works well if
the bar is connected higher in the lighter pendulum. Just fix the bar
to the strings making loops in the strings and search the best position).
> The secondary winding having many more turns then the primary, converts
> all available current to voltage (ohms law).

No. No Ohms' law here.

> If I look at this from a different angle
> however (for example; audio circuits), most of the circuits contain a
> capacitor also on the secondary winding to adjust the resonance on that
> side of the circuit too. However in many designs of Tesla coils I do not
> see this (cap on the secondary). Why is this ?

It is there, as the self-capacitance of the secondary coil and the body
capacitance of the top terminal.

Antonio Carlos M. de Queiroz