Re: Capacitance of Archimedean coil

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <teslalist-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

You can approach the problem of finding an analytical solution (i.e. an
equation) for the capacitance of something a lot of ways. You can start with
an approximation.. i.e. cylinder above a flat plane, or (in the case of the
flat spiral) flat plate above a flat plane.  Working out an equation that
works for some small "section" in the middle is usually fairly easy (in the
case of a TC secondary, say, 1 horizontal slice of the secondary, which
looks like a small ring above a ground plane), but it won't deal with
"fringing effects" at the edges/ends.
These days, with computers, it's probaby easier to use numerical techniques
and grind the number out, like E-Tesla does.

One disadvantage of the numerical approach (or, looking up the numbers in a
table) as opposed to the analytical equation approach is that the equation
might (!) give you some insight into the underlying physics.  If you saw a
table of forces between two charged objects as a function of their charge
and distance, you might not immediately happen upon thinking about the
inverse square law, which is a fairly important thing.

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Sunday, March 30, 2003 6:33 AM
Subject: Capacitance of Archimedean coil


 > Original poster: "Marko by way of Terry Fritz <teslalist-at-qwest-dot-net>"
<moyson-at-tig-dot-com.au>
 >
 > Hello all!
 >
 > The Medhurst formula calculates a cylindrical coil capacitance. Does this
 > formula has come about purely from experimental means, or can it be
derived?
 >
 > I am looking to calculate the capacitance of a flat spiral coil.
 > I have not been able to find a formula for capacitance of other coil forms
 > like the flat spiral coil.
 > Does anyone know of this?
 > Or is there a method for deriving a coil capacitance??...my textbooks are
 > not helping...
 >
 >
 > Thanks,
 > marko.
 >
 >