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Re: Tesla coil formula -- oops correction



Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Shaun,

Another thing about the physics equation that should be mentioned is that it neglects the end effect of the selenoid (get some leakage toward the ends). The equation will overestimate the actual inductance to some extent..

Gerry R.

Original poster: Shaun Epp <scepp@xxxxxxx>

Oops I made a error on my first post,  Here's the correction

The actual equation for Inductance that is written in physics books that
I've seen is:

L = u N^2  A              which clearly shows that inductance is
     -----------             proportional to the the area of the coil
            l                      (A), the number of  turns squared (N),
                                  and inversely proportional the the
                                  lenght of the seleniod (l)
                                  u = 4 pi 10^-7 (mu)

A = pi r^2                  r is radius of coil

so --- 2 pi r N is approaximatly wire length, if you ignoring the length of the
                       selenoid.

(wire length)^2 = (2 pi r N)^2 + l^2   is probably more accurate.

Your equation works, but It wasn't designed to show that wire length was proportional to resonance. A person could stuff anything into an equation if they divide out what doesn't belong. (4 pi)

Shaun Epp


----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Monday, December 05, 2005 4:59 PM
Subject: Re: Tesla coil formula


Original poster: Jared E Dwarshuis <jdwarshui@xxxxxxxxx>

I'd like to respectfully suggest that that may be because you have
to effectively introduce a fiddle factor by adding a specific amount
of terminal capacitance to make it work (and what's worse, adjust
that capacitance for a specific coil geometry). We have come full
circle. Discovering that hidden factor in a plethora of wire length
equations (all of which were sworn as gospel by their proponents)
back in the eighties was where I began my investigations which led
to my adopting the now popular L and C approach.

Malcolm

Hi: Malcolm

For an air cored inductor, the inductance, as derived by Maxwell's
equations can be written as:

L = u ( wire length )Sqrd / (4pi l )

Prominent is the wire length, a sadly neglected geometry.


Jared Dwarshuis