RE: Variable Capacitance and Inductance

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

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

Hi Dave,

>'we' (as an engineering culture) have gained much knowledge, have better
instruments. since then.

Wow! And until a couple weeks ago nobody seemed to care that Wheeler's
formula was outputting 1000 inches (and many probably still don't care.)  It
was a point clearly made by some that we just don't have any formulas that
give direct capacitance or direct inductance.  Why can't our "better
instruments since then" give us exact inductance and capacitance
measurements?  Could it be because inductance and capacitance are variable;
just as Tesla noted?

Dave P.>The variation in capacity of an isolated body (more or less
isolated, since altitude above earth seems mentioned) is well known, falls
out from the basic maths, and was, i believe, known at the time, and
earlier.

Malcolm W.>The assertion that the capacitance of the terminal increases with
height simply doesn't stand to reason (unless it was just a few inches from
the coil to begin with - mutual shading). In elevating it (outdoors), he is
moving it further away from ground (closer to the ionosphere for sure, but
an absolutely trifling amount by comparison).

Now how come this is well known to you and Malcolm doesn't agree?  Are the
engineers in our culture that divided over what is true and what is not
regarding variable capacitance and inductance?

I posted this article by Tesla on the USENET and a guy responded with about
a dozen different ways that inductance of a coil can be affected.  BTW, one
of his comments was quite interesting.  He said that by intertwining a
solenoid with another solenoid and applying a voltage the effective
inductance of the coil can be tuned.

>Were the 'rewritten' formulas published, tested, used? Are they used?

If you have seen formulas that require the date, time, altitude, longitude
and latitude to be input, then you will see Tesla's suggested formulas.  I
haven't seen them.  But if there is any truth to these factors, I predict
somebody will eventually write new formulas.

Dave