Nikola Tesla Books
Books written by or about Nikola Tesla
Colorado Springs
Nov. 8, 1899
Table of inductances prepared from preceding readings.
| Two primary turns in series | 230,945 cm. | 0.000230945 H |
|---|---|---|
| One of the primary turns | 57,736 " | 0.000057736 " |
| All connections to condensers and breaks as used | 5004 " | 0.000005004 " |
| All connections plus one half turn of reg. coil (first turn) | 5774 " | 0.000005774 " |
| All connections plus the whole first turn of reg. coil | 6544 " | 0.000006544 " |
| " " 1 1/2 " " | 7314 " | 0.000007314 " |
| " " 2 " " | 8084 " | 0.000008084 " |
| " " 2 1/2 " " | 8854 " | 0.000008854 " |
| " " 3 " " | 10,009 " | 0.000010009 " |
| " " 3 1/2 " " | 11,164 " | 0.000011164 " |
| " " 4 " " | 12,319 " | 0.000012319 " |
| " " 4 1/2 " " | 13,474 " | 0.000013474 " |
| " " 5 " " | 15,158 " | 0.000015158 " |
| " " 5 1/2 " " | 16,842 " | 0.000016842 " |
| " " 6 " " | 18,526 " | 0.000018526 " |
| " " 6 1/2 " " | 20,210 " | 0.000020210 " |
| " " 7 " " | 21,894 " | 0.000021894 " |
| " " 7 1/2 " " | 23,578 " | 0.000023578 " |
| " " 8 " " | 25,262 " | 0.000025262 " |
| " " 8 1/2 " " | 26,946 " | 0.000026946 " |
| " " 9 " " | 28,870 " | 0.000028870 " |
| " " 9 1/2 " " | 30,794 " | 0.000030794 " |
| " " 10 " " | 32,718 " | 0.000032718 " |
| " " 10 1/2 " " | 34,642 " | 0.000034642 " |
* This table is close enough for all general estimates.
After 10 1/2 turns the increase is 3850 cm. per turn so that the inductance of 10 1/2 + n turns + conn. will be 34,642 + n x 3850 cm. With the entire coil in, there are 23 1/2 turns having 84,692 cm. or 0.000084692 H.
In order to test the accuracy of the preceding measurements, readings of the e.m.f. across the two primaries, connections and the regulating coil - all joined in series - were taken repeatedly and in as rapid a succession as was found practicable, the number of the turns of the regulating coil being varied after each set of readings. The diagram below shows the connections of the various inductances while the readings, reduced to the same e.m.f. across: [the two primary turns + connections + 1/2 of one turn of the regulating coil + flexible cable] are given in table below:
268
November 8
The primary inductance values cited are from November 5th. The other values given in the table do not agree with those derived from the measurements of October 30th. Also, earlier data do not include values for half a turn of the regulating coil. It must therefore be concluded that the measurements from which the tabulated values were calculated are not described in the diary.
It seems that in measuring inductance from voltage, current, frequency and resistance Tesla had difficulty because of unreliability of the frequency determination. He therefore used the voltage ratio, when it is only necessary for the frequency to be constant. By this method he measured the inductance of the regulating coil plus connections, for various numbers of turns.
November 8
He attaches the table of calculated primary and regulating coil inductances plus that of the connections as a function of number of turns. The values for the primary are those of Nov. 5. Other values given in the table do not match those obtained on the basis of measurement data of Oct. 30. Also in previous data the values for the regulatory coil turns halves are not given.
From all this it follows that the measurement results from which the calculated values are obtained and which are shown in the attached table are not given in the notes.
It seems that Tesla was not satisfied with the inductance measurements on the basis of voltage, current, frequency and the resistance due to uncertainty of determining the frequency itself. That is why he applied the method of voltage ratio where it is only important that source frequency is not changed during the measurements.
By this method he performs the measurements in order to determine the regulating coil and the connection inductance for the various number of turns of the coil.
