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Re: How (does) voltage rise(s?).

Original poster: robert heidlebaugh <rheidlebaugh@xxxxxxxxxxxxxx>

Chip: The shape of the primary is the choice of the builder. The solinoid
coil delivers the most energy to the secondary, but causes the most
problems. This shape is most often used on tube coils. When used with
discharge coils it is subject to racing sparks down the secondary and arcing
between the primary and secondary. It can be relieved with insulation
between the primary and secondary and elivating the secondary above the
primary or making the spacing between the primary large to minimize the
problems. Tc builders use this shape in multiplier coils , This shape is not
recomended for beginning coilers because it requires a lot of
experimentation to get it right. The flat primary has the least coupeling
and the least problems. It is the most popular shape. The inverse cone is a
good compromise between the two , but more dificult to build , and make
stable. I use all three, I like the cone secondary and solinoid primary for
high voltage. I like the flat primary and solinoid secondary for long
sparks, I use cone primary  and secondary for compact size and high voltage.
Most people want big flashes and dont care what the voltage is.
\     Robert   H

> From: "Tesla list" <tesla@xxxxxxxxxx>
> Date: Sun, 16 Jan 2005 21:06:12 -0700
> To: tesla@xxxxxxxxxx
> Subject: How (does) voltage rise(s?).
> Resent-From: tesla@xxxxxxxxxx
> Resent-Date: Sun, 16 Jan 2005 21:06:16 -0700 (MST)
> Original poster: Chip Atkinson <chip@xxxxxxxxxx>
> Greetings all,
> My dad came over to help me work on a little tesla coil this afternoon.
> I was explaining how the voltage rises in the secondary and kind of came
> up with an explanation. It seems to make sense so I thought I'd put it in
> the pool of knowledge and see if it floats so to speak.
> The first question was why one wants to loosely couple the primary and
> secondary. Why not just have a solenoidal primary enclosing the
> entire secondary rather than a pancake or conical primary?
> I drew out what I figured would be the magnetic field from a solenoid and
> a pancake. The solenoid field is more or less uniform within the coil
> itself and loops from the ends of the coil back to the other end. Kind of
> like a "tall" torus.
> With a pancake coil, the field is like a regular torus with the bulk of
> the magnetic field affecting the base of the secondary, as opposed to a
> solenoidal primary where the the field would entirely enclose the
> secondary.
> With the uniform solenoid field the secondary is just subject to turns
> ratio and the voltage doesn't rise any more than that. There is no
> "whipping action" where the voltage is more or less free to rise as there
> is when only the base is driven as by a flat coil.
> The next question in my mind is *why* does the voltage rise? How can I
> think of it?
> Here's what I came up with -- the electrons are like a gas. If you have a
> column of air, say, and drive it at the base you can actually get louder
> (greater voltage) output if you drive it at the resonant frequency. For
> example, a didgeridoo. The thing though was that doesn't the oscillating
> medium have to have momentum to resonate? That's where I figured the
> inductor of the secondary came into play. An inductor conceptually gives
> electrons momentum -- they keep flowing in their current direction and
> resist changing directions.
> The purpose of the capacitor at the top is mainly to store up this
> pressure wave of electrons until the pressure (voltage) at the top reaches
> the breakout voltage. Then once it's broken out, the electrons are
> suddenly released and produce a more energetic streamer or spark. The
> reason for not just having a bare wire at the top is that the point effect
> of the bare wire allows the breakout voltage to be too low. The reason
> that we don't put a toroid the size of a box car on a 3" coil is that a
> toroid that big would "soak up" all the surplus electrons and spread them
> over such a large area that the voltage would actually drop from what it
> was right where the wire attached to the toroid.
> Does this make sense? Is it right more or less? What I'm trying to do is
> figure out how to understand and thus explain it. I'm not worrying so
> much about accurately predicting the actual values but more in
> understanding the concepts about what's going on.
> I swear I haven't been smoking. :-)
> Chip