Re: Variable Capacitance and Inductance

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

Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi Jan, Dave,

Regarding the box experiment. If the cap is in a sealed box, it is still
susceptible to temp
variations of the boxes surroundings. The capacitance "will" change as the
box is exposed to
various locations. I suspect temperature and humidity are the key players
for these changes in
capacitance. Recently I've taken measurements of my main cap, and the main
cap has changed by a
factor of ~4nF. What was measured at 61nF grew to 65nF (same meter and
leads) taken one day
following a 2 day cycle of rain (it's possible the meter is the one
affected?). Possibly premature,
but I feel the increase in humidity has affected the cap by way of the
objects around it, and those
objects were affected by the rain and temp. Unfortunately, I didn't see the
capacitance change
coming and therefore didn't log humidity or temp data to coincide.

Take care,
Bart

Tesla list wrote:

> Original poster: "David Thomson by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <dave-at-volantis-dot-org>
>
> Hi Jan,
>
> >Yes, L and C do vary, if the surroundings of the place of measurement are
> changed. If the surroundings remain absolutely fixed, exactly, L and C won't
> change.
>
> Thanks.  That's the point right there.  Inductance and capacitance are
> affected by stellar activity, geomagnetic activity, house wiring, and the
> abundance of metal in our society and even in the ground.  Atmospheric
> conditions will affect the electrostatics of a coil and capacitor, but there
> are many influences that affect inductance and capacitance.
>
> The observations of Tesla and others on this list of variable inductance in
> there coils is not necessarily the result of faulty equipment, measuring
> techniques, or humidity.  It has taken a while to get to this point, but I
> think we may be there.
>
> When the environmental factors contributing to variable inductance and
> capacity are acknowledged then that opens the doors to further knowledge in
> our art of coiling.  There are certain designs of coils that are more
> susceptible to environmental changes than others.  The combination flat
> spiral and secondary coil that I use produces a fluctuation in inductance
> readings between 5mH and 30mH each second when my house power is on.  Even
> this fluctuation varies over time.  When I measure the inductance of a very
> large flat spiral coil, the inductance meter won't work.  These observations
> are not equipment malfunctions but measurements of real phenomenon that are
> worthy of further study by coilers.
>
> Based on the limited data I have collected so far, house current appears to
> be the most influential factor that alters inductance and capacitance in a
> dwelling.  When my combination coil is operating I see fluctuations in its
> functioning as well.
>
> >Here's an experiment for your (maybe for others too!):
>
> This is a good suggestion.  I have also planned a similar experiment where a
> capacitor and inductor would be stored in evacuated jars and measured for a
> period of time.  This would eliminate the humidity and temperature factors.
>
> Dave