Re: capacitance (fwd)

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

Original poster: Tesla List Moderator <mod1-at-poodle.pupman-dot-com>



---------- Forwarded message ----------
Date: Fri, 16 Jul 2004 22:49:48 -0300
From: Antonio Carlos M. de Queiroz <acmdq-at-uol-dot-com.br>
To: Tesla list <tesla-at-pupman-dot-com>
Subject: Re: capacitance

Tesla list wrote:
> 
> Original poster: "Anthony" <ant17-at-optushome-dot-com.au>
> 
> How accurate is that formula

This formula ignores the "end effects" at the edges of the plates.
If the plates are much wider than the thickness of the dielectric,
the error is insignificant. But for high-voltage capacitors with
low capacitance and thick dielectric the error is significant.
Taking measurements from two capacitors it is possible to determine
both the dielectric constant of the material and a margin to be added
to the dimensions of the plates to take the end effect into
account. I have implemented the necessary calculations in the
program Elcal, available at http://www.coe.ufrj.br/~acmq/programs.

Antonio Carlos M. de Queiroz