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Re: LC and Misc.

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

Hi Jared,

Original poster: Jared E Dwarshuis <jdwarshui@xxxxxxxxx>

From: Jared Dwarshuis

Consider a given length of wire and a target LC frequency. We could
wind a stubby inductor or a skinny inductor.

If we wind a skinny inductor, our inductance will be very low and our
top end capacitance will be rather large.

If we wind a stubby inductor, our inductance will be high, but our top
end capacitance will be very low.


OK, if we use the simplified equation  L=uo*N*A/h,

where uo = permibility of free space
         N = number of turns,
         A = cross sectional area of coil
          h = height of coil

assume close wound,

and substitute N= Wl/(2*pi*r) A = pi*r^2, and h = N*Wd

where Wl  = wire length
         Wd = wire diameter
           r   = radius of coil

we get: L = uo * Wl * r / (2*Wd). If Wd and Wl are constant, the stubby inductor will have more inductance as compared to the skinny one.

A stubby inductor has a very high self capacitance. In theory you
could make a coil with no top end at all. (maybe someone out there has
done so?)

If we take two spheres at the same voltage (one with small radius and the other with larger radius). The E field on the smaller one will be greater at the surface (due to smaller ROC) and drop off sooner (smaller reach) as one moves away from the sphere. The smaller sphere will also require a smaller charge to reach the same voltage. So, I guess the self capacitance of the coil is proportional toWl and the radius of the coil (first order affects maybe).

I think, like you say, one could use that length of wire and choose the radius where the self capacitance and the inductance gives the specified frequency. If the specified freqency was achieved by self capacitance only, I think, performance would suffer greatly since not all of the self capacitance is available to support streamer growth on a TC discharge and without a "real" top load, breakout would be at a lower voltage and the E field "reach" would not be as great. But then again, I'm not sure of your context nor your point.

Gerry R.


Dr. Resonance has, in the past, posted information on the number of
turns and H/D ratios. His guidelines are based on a lot of
experience.