Re: New Inductance Formula

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

Original poster: "harvey norris by way of Terry Fritz <twftesla-at-qwest-dot-net>" <harvich-at-yahoo-dot-com>


--- Tesla list <tesla-at-pupman-dot-com> wrote:
> Original poster: "David Thomson by way of Terry
> Fritz <twftesla-at-qwest-dot-net>" <dave-at-volantis-dot-org>
> I have tested this formula with three solenoid coils
> that I had already wound. 
> The results are close.  As I mentioned, I feel the
> formula can be improved upon
> to give a more accurate result.  This will be done
> by taking into account the
> impedance of the coil, something other formulas do
> not do.  
Dont see why they should, since inductance is a
(generally)constant, but impedance is not, it will
have a different value for every different imposed
frequency according to Z= sq rt{X(L)^2 + R^2} where
impedance is usually approximated to be close to the
value of X(L) when X(L) >> R.

To see why the impedance is not constant we then
merely go to the definition of X(L)= 2 (pi)*f *L.

So we se that 2 pi L is constant, but the reactance
X(L) will then be proportional to f, the imposed
frequency.

Both inductance and capacitance were also expressed in
terms of length in Teslas day, where the CSN always
shows inductance recorded in cm, where the conversion
factor is 10^9 cm = 1 henry.

See H LTranstrom/Turn of the century definitions for
cm's of L and C quantities

http://groups.yahoo-dot-com/group/teslafy/message/14
(For capacity)
The capacity of isolated spheres are found 
to vary as their radii. A sphere having a radius of 1
centimeter, hung up in space at an infinite distance
from any other conductor;has unit electrostatic
capacity;so the capacity of spheres in electrostatic
units can be given directly from their radii in 
centimeters. Consequently, a sphere having a radius of
9 times 10 to the 11th power cm has a capacity of one
farad, and a sphere of 900,000 cm. radius equals one
microfarad; hence some authors write 1 microfarad as
900,000 cm of capacity. 

Now concerning the use of inductance defined in terms
of cm , Transtrom also goes into this on pg 80-82. The
inductance of a circuit is sometimes expressed in
centimeters, one of the cgs units or absolute units.
By definition a circuit has a self induction of 
one henry when it generates a counter emf of one volt
when the current is varied at a uniform rate of one
ampere per second-- that is the circuit cuts 10^8
lines per second: so a circuit of one turn 
which has a flux of one Weber (10^8) when one ampere
is flowing through it, has an inductance of one henry.
One volt then represents a movement of a single
conductor of 100,000 cm per second across a 
unit field (1 line per square cm) In this way the emf
in volts can be given the dimension of length, namely
10^8 cm. As a circuit of one henry inductance
generates a counter emf of 1,000,000,000 centimeters 
when a change of one ampere, or one tenth unit of
current per second, it is plain that the counter emf
would be ten times as high, or ten volts
(1,000,000,000 cm) when the rate of current change per
second is unity (or ten amps per second) Therefore one
Henry of inductance is given the dimension of
1,000,000,000 cm. In a circuit of only one 
turn the inductance in centimeters can be directly
obtained from the number of lines enclosed when a
current of 10 amperes is flowing through the
conductor. The Henry was once called the secohm,
because a circuit having an inductance of one henry
would only permit a rate of change of one ampere per
second when the impressed current had an emf of one
volt, and as the counter emf acted as one ohm
resistance, we see from this that the inductance can
be expresssed in ohms. The henry has also been called
the quad, or quadrant because in the metric system a
quadrant of the earth from the equator to the pole 
equals approximately 10^9 centimeters. Both terms
mentioned above are now quite obsolete.  HDN

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