Capacitance of a cylinder coil
From: Mark S. Rzeszotarski, Ph.D. [SMTP:msr7-at-po.cwru.edu]
Sent: Wednesday, April 08, 1998 7:28 AM
To: Tesla List
Subject: Re: Capacitance of a cylinder coil
Regarding the Self Capacitance of an air core cylindrical coil
The table I posted a long time ago on the self capacitance of
solenoidal coils is directly from the original Wireless Engineer papers by
The formula works very well for the case of a tesla coil, provided
that one end of the coil is grounded and that the wire has been wound on the
coil with uniform spacing.
If the wire spacing is nonuniform, the formula no longer applies.
For example, consider the case of two coils with the same height and
diameter, but each wound with a different gauge wire. If you stack them one
on top of the other, ground one end, and measure the resonant frequency, you
get one reading. Next, swap the coils so they are stacked in the reverse
order. Measure the resonant frequency and, voila, it is not the same, even
though the total inductance, total height, and diameter are identical.
Medhurst's formula no longer applies!
Mark S. Rzeszotarski, Ph.D.