# [Fwd: [Fwd: Re: Variable Capacitance and Inductance]]

```Original poster: "davep by way of Terry Fritz <twftesla-at-qwest-dot-net>" <davep-at-quik-dot-com>

Hi Dave:
Tesla list wrote:

> 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.

They do give trends.  There is a differnc between
absolute accuracy and trends.

> Why can't our "better instruments since then" give us exact
> inductance and capacitance measurements?

They do.  Or at least the best instruments, rigorously
used, do.

> Could it be because inductance and capacitance are variable;
> just as Tesla noted?

Both are varied by surrounding effects.  'nothing'
(on earth) exists in 'free space'.  In general Tesla
was not measuring capcaitince, but looking at some
other effect and assigning a variation to change
in capacitiance.  For the values (small) worked with
by Tesla (when working with elevated capacities),
the measurement, with techniques available, is
tricky.

> 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?

We are both 'describing the same elephant', from
different perspectives.

> 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.

cf 'magnetic amplifier'.

>>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.

If...

Also: 'a month of 16 hour days' (from another thread)
tends to lead to fatigue, and poor performance.

One might repeat the experiment & see what results
are obtained.
best
dwp

```