Nikola Tesla Books
Books written by or about Nikola Tesla
to foregoing and calling L3 the inductance of the two primaries + connections + flexible cable + 1/2 turn of regulating coil:
L3 = $! {105 \over 102} $! x L = $! {105 \over 103} $! x 230,945 = 237,738 cm.
Hence the inductance of all these mentioned connections is L3 - L = 237,738 - 230,945 =
| = 6793 cm, for | { | connections proper 1/2 turn regulating coil, flexible cable in reg. coil. |
Note: A small error is often caused by the changing position of the flexible cable which makes the readings for a small number of turns larger (slightly).
Colorado Springs
Nov. 7, 1899
Further experiments for the purpose of ascertaining the capacity of the structure of the iron pipe by resonance analysis. Two sets of readings were taken: one set with new extra coil the other with coil 346 turns wire No. 10 on drum 14" diam. The readings were as follows:
With new extra coil
| Capacity in primary exciting circuit total: | Inductance in primary circuit. Turns of regulating coil + conn. | Analyzing spark on terminals of excited coil. |
|---|---|---|
| $! {{(8x36)-2} \over 2} $! = 143 bottles = 0.1287 mfd | 22 + conn. | 2 5/16" |
| $! {{(8x36)-2} \over 2} $! = " = 0.1287 mfd | 8 + " | 3 3/4" |
With experimental coil described
| Capacity in primary exciting circuit total: | Inductance in primary circuit. Turns of regulating coil + conn. | Analyzing spark on terminals of excited coil. |
|---|---|---|
| $! {{(3x36)-2} \over 2} $! = 53 bottles = 0.0477 mfd | 15.75 + conn. | 4" |
| $! {{(3x36)-2} \over 2} $! = " = 0.0477 mfd | 3.5 + " | 3 1/8" |
*Note: The first readings are of course with, the second without structure in each case.
*Note: Readings were also taken on this occasion with coil wound on 10 5/16" drum before described (550 turns) but merely for the purpose of comparing the inductances
264
November 6
Tesla carefully measured the capacitance of the aerial pole by the resonance method, from the known inductance of the 550-turn coil (see September 8th) and known frequency of the oscillator, with two measurements, one with and the other without the capacity to be measured. He did not make use of his earlier results for the inductance of the regulating coil and connections from October 30th, although he could have done. A calculation check shows that the results of October 30th were rather high (by as much as 10% for 2 1/8 turns of the regulating coil), but Tesla probably thought that the new procedure was better and so did not use the old results. An analysis shows that if the old values had been used the final result would not have been essentially affected, so that Teslaâs conclusion that the measured capacity of the pole was less than the theoretical value of November 5th remains valid.
From the relatively lengthy discussion following the measurements it may be seen that Tesla expected just the opposite. As usual when his expectations were not fulfilled, he considers ways for getting more reliable results.
November 6
He measures the capacitance of the structure with the sphere by means of the resonant method very carefully, on the basis of known coil inductance of 550 turns (please see Sept. 8) and known oscillator frequency, from two measurements he finds the desired capacitance. The first measurement is without connected structure and the second with it. The resonance he determines on the basis of the maximum spark and the frequency on the basis of inductance and capacitance in the oscillator circuit. In a series of separate measurements he determines the value of a regulating coil as well as the inductance of the connections by following a new procedure.
The primary coil, and the regulating coil with connections as in the measuring circuit is connected to the source of low frequency (most probably as previously 140 Hz) and it measures the voltage ratios shown in the figure. From the previously determined primary coil inductance and the voltage ratio, the total inductance of the connections and regulating coil is obtained. It is interesting that he did not use the results for regulating coil inductance and the inductance of connections obtained on Oct. 30, as he could use them. The calculation check of the previous result indicates that the values obtained on Oct. 30 were somewhat higher (even more than 10% higher for two 2-1/8 regulating coil turns), considered that the newest procedure is better and that is why he did not use the old results. The analysis indicated that even with the old values final results would not change much and Tesla's conclusion is still valid in that the measured value of the structure capacitance is smaller than theoretical value obtained on Nov. 5. From Tesla's relatively long explanation after he performed measurements, it could be seen that he expected exactly the opposite effect. As always so far when his expectations were not met, he continues the considerations about further steps for the purpose of achieving more reliable results.
November 7
Measurement of the capacity of the structure at two frequencies was intended to demonstrate the reduction of effective capacity with increasing frequency. Tesla did in fact obtain a small difference, but it is dubious proof considering the accuracy of the measurements. The frequency difference was quite large, from 50 kHz to nearly 250 kHz (using âextraâ and âexperimentalâ coils).
November 7
He measures the structure capacitance with two coils, one is a new "additional coil" (please see Oct. 31). The results are similar to those of Nov. 6. An attempt to measure the structure capacitance at two frequencies was intended to prove that the capacitance is reduced when the frequency is increased. Tesla obtained a small difference but without that it is a reliable proof when we take in account the measurement accuracy. Otherwise the frequency changed substantially; from approximately 50 Hz to almost 250 KHz{during the period of obtaining the measured results with the "additional" and "experimental" coil).
