# [ 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:

> Hi Dave,

>>There is a difference between absolute accuracy and trends.

> Is this a euphemism for saying you agree that inductance
>and capacitance are variable?

My point was that measurement techniques which may
not yield absolute accuracy (1.0000 inch) may still
be able to tell that something is bigger than something
else, or, if changing, is changing in a given direction.

>>>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.

> Can you give me a reference?

Any course in physics, electrical engineering, etc.

> Does this mean you believe a coil measured with one of these
> instruments at one time will measure the exact same
> inductance at all other times?

IF all other things are the same.  And belief does
not enter into it.  Consider the precision routinely
achieved in, eg space flight.  (barring gross human
error: the feet/meters issue...)

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

>>Both are varied by surrounding effects.

> If they are variable, then how do these accurate measuring
> devices get the same exact result each time?

By making sure the surrounding results are the same.
cf any cal lab.  Any course in measurement technique.

> Even if you are saying the machines are accurate and are
> measuring exact variations in inductance, that still agrees
> with Tesla's assertion that capacitance and inductance are
> variable.

I suggest studying circuit theory, the difference between
'real' and ideal components.
Also (and more to the point) variation in the _measured_
value is different than variation in the device.
More to the point:
Tesla asserted that he observed changes
LARGER IN SIZE
and
OPPOSITE IN DIRECTION
from everybody since (and some/all) before.

>>'nothing'(on earth) exists in 'free space'.

> Perhaps the more relevant observation is that "free space" has
> inherent permeability and permittivity;

Which are well known, well measured, well understood and
have DIFFERENT effects, in magnitude and direction from
(some of) those Tesla reported.

> the stuff that "makes" inductance and capacitance.  This is why
> inductance and capacitance can be variable for a material object
> such as a coil or capacitor.

Put either in a shielded box.
Do the measurement.

> The inductance and capacitance of material objects is not entirely
> dependent on the characteristics of the object, but also on the
> characteristics of the environment in which it exists.

1) CF above.
2) The environmental effects are well known, exhaustively
studied and different from those Teal's observations require.

>>In general Tesla was not measuring capcaitince, but looking at
>>some other effect and assigning a variation to change in >>capacitiance.

> That sounds just like how the "best instruments" you reference,
> work.  As far as I know, there is not a machine on the face of
> this planet that measures inductance or capacitance directly.

There are a few, used to calibrate the standards used
by the rest.
They get closer than those available to Tesla.

>>For the values (small) worked with by Tesla (when working
>>with elevated capacities), the measurement, with techniques
>>available, is tricky.

> No more than it is today.

Today we have feedback techniques to stabilize
oscillators, amplifiers and temperatures.
We have crystals to stabilize frequencies.
We have computers to average out (invisibly)
drift.

> Tesla built his own LC meters.  We buy them off the shelf.

Better ones.

> All that does is make LC measurements available to less
> qualified people such as myself.

........

>>, 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.

> Well then, since you and I agree that capacitance can be variable,

The magnitude, cause, and direction of that variation
likely you and I do not agree on.

> and you and Malcolm see "the same elephant," then we must all be
> in a agreement?

...and it was presumptuous of me to say that Malcolm
was in agreement with me...  (I think we are, or
are close.  i could be wrong.)

> Somehow I don't think this thinking would be widely accepted.
> Can you give a clearer explanation as to how Malcolm's and your
> views are the same?

cf above on presumption.  With that in mind:
We both point out that capacitance varies.  Malcolm
goes further, and points out that Tesla's observations
appear opposite DIRECTION and different in SIZE from
all others.

>>	cf 'magnetic amplifier'.

> Ahh, yes.  Thanks.  I do remember reading about that.

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

> The truth is that Tesla went nearly his entire life at that schedule,
> starting with high school.  Although Tesla did have several bouts with
> disease and fatigue, he was quite productive for most of his 86
> years; right up to the end.

For the last 30 odd years, 'production' was limited
to writing speculation for magazines.

> Other men, such as Thomas Edison, had difficulty keeping up
> with Tesla's schedule.

Edison scholars would disagree.  Here is likely not
a good place to debate it.

> Tesla adhered to the 16 hour day schedule the entire time he
> was in Colorado Springs.  I don't think that improvement of brush
> motors, the invention of all AC motors,

THAT, too, is subject to debate.
Many yes, all?

> the invention of high voltage oscillators, and several other
> notable inventions are the result of fatigue and poor
> performance.

...all of which he did BEFORE going to Colorado Springs...
Also when he was YOUNGER.  Tolerance for this sort of
thing varies with age.

>  Your unqualified criticism of Tesla is much like

We have, i believe, different definitions of 'unqualified'.
Also of 'criticism'.
I simply cite what can be found in any text on human
factors.  (I take Tesla to have been human...).

> Richard Hull's, it is based merely on personal opinion.

cf above.
best
dwp

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