Re: Inductance of a conical coil

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Original poster: "Godfrey Loudner by way of Terry Fritz <teslalist-at-qwest-dot-net>" <ggreen-at-gwtc-dot-net>

Hello Antonio

Well the Mathematica software failed to numerically integrate the
Neumann integral last night. I thought I was doing Mathematica
a favor by shrinking the limits of integration to (0, Pi/2) by a change
of variables. This caused the cosine and sine functions to oscillate
wildly on the short interval. The resulting convergence was so slow
that Mathematica gave up the task. I'll have to make a change of
variables to get the trigonometric functions completely out of the
integral. I used parametric representations for the spirals of
both the primary and the secondary. I suppose the next problem
will be the long intervals for the integration. This must be why you
broke the conductors up into 20 segments. But I'm really
surprised that Mathematica balked at the form of the integral I
presented. After all, Mathematica will compute Pi to 30,000
places on a PC in a few moments!

Godfrey Loudner

 >I think tonight I'll set up
 > the Neumann's integral for Bart's old 12.75" coil, using a
 > parametric representation of the spiral. Of course I'll use
 > filaments for the conductors. I want to see if the powerful
 > Mathematica software will numerically integrate the Neumann
 > integral.
 >
 > Godfrey Loudner