Re: Variable Capacitance and Inductance

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

Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <twftesla-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:
> 
> Original poster: "David Thomson by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <dave-at-volantis-dot-org>

> Continuing the investigation of this astonishing phenomenon I observed
that the
> ca­pacity varied with the elevation of the conducting surface above the
ground,
> and I soon ascertained the law of this variation. The capacity increased
as the
> conduct­ing surface was elevated, in open space, from one-half to
> three-quarters of 1 per cent per foot of elevation. In buildings, however, or
> near large structures, this increase often amounted to 50 per cent per
foot of
> elevation, and this alone will show to what extent many of the scientific
> experiments recorded in technical liter­ature are erroneous. In
determining the
> length of the coils or conductors such as I employ in my system of wireless
> telegraphy, for instance, the rule which I have given is, in view of the
above,
> important to observe.

If Tesla really wrote this, he had serious problems with the quality of
his capacitors. Capacitance and inductance depend on geometric factors
and
on the medium around the conductors (magnetic permeability for inductors 
and dielectric constant for capacitors), and are only precise if the 
geometry is precise and invariable and the medium is also fixed. 
The text doesn't specify the capacitance of what is being discussed. 
The figures look quite excessive even for very bad capacitors. 
Makers of electronic parts for airplanes of space vehicles (or tall 
buildings) would be in serious difficulties if the parameters of their 
circuits were so variable.

Antonio Carlos M. de Queiroz