Nikola Tesla Books
Books written by or about Nikola Tesla
period of the system remained in each case the same the products of the capacity and self-inductance in primary remained constant also. Now the capacities in the primary in the succeeding experiments being known or exactly measurable, the various values of inductance in primary were obtained from the relation:
L1C1 = L2C2 = L3C3 = etc.
The period of the secondary system was Ts = $! {{2 \pi \over 10^{3}} \sqrt{L {C_{s}}_{1}}} $!.
The inductance of coil 344 turns being about 6 x 106 cm. and the average value for Cs1 from a number of readings with different values of inductance and capacity in primary circuit being 34.9 cm., the period of secondary or excited circuit was thus given.
A reading was now taken at random and resonance was obtained with constants in primary circuit as follows:
| Capacity in primary circuit | Inductance in primary |
| $! {36 \over 2} $! = 18 bottles = 0.0162 mfd | 4 $! {13 \over 16} $! turns + conn. |
from this the period of primary circuit was:
Tp = $! {{2 \pi \over 10^{3}} \sqrt{{0.0162 \times L}}} $! L being the inductance in primary
Now Tp = Ts or 0.0162 x $! {L \over 10^{9}} $! = $! {{6 \times 10^{6}} \over 10^{9}} \times {34.9 \over { 9 \times 10^{5}}} $! and from this we get L in centimeters:
L = $! {{6 \times 10^{6} \times 34.9} \over {9 \times 10^{5} \times 0.0162}} $! = $! {{34.9 \times 6} \over{9 \times 0.0162}} $! = $! {698 \over 0.0486} $! = L = 14,362 cm.
by resonance method.
Now from table prepared:
| Inductance L = 4 $! {13 \over 16} $! + conn. | = | { | Inductance 4 1/2 turns + conn. | = 13,474 cm. |
| Inductance 5 turns + conn. | = 15,158 cm. | |||
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| Ind. of 1/2 turns | = 1684 cm. | |||
| Ind. of 1/16 turns | = 210.5 cm. | |||
Ind. of 5/16 turn = 5 x 210.5 = 1052 cm approx.
Consequently inductance L = Ind.{4 1/2 + 5/16 turn+ conn.} = 4 $! {13 \over 16} $! turn + conn. = 13,474 + 1052 = 14,526 cm.
Agreement fairly close, within about 1%. This shows readings are reliable.
300
November 24-26
To check the values for the inductance in the primary circuit (of the oscillator) which he had earlier measured by the voltage, current and frequency method (see October 30th), Tesla repeats these measurements using the resonance method. He described the procedure on October 21st and made some measurements but did not follow them up with calculations. This time he made both measurements and calculations, but only for one LpCp combination. He compares them with values derived from the table given November 8th using linear interpolation. He was probably satisfied with the agreement, and did not make further checks. He had measured the capacity of the same structure, but without the protective cap and using the “extra” and “experimental” coils, on November 7th. On November 12th he had made similar measurements using the 1314-turn coil. In the 26 November entry he refers to the result of 7 November with a new “extra” coil. There is also one more result obtained with an “extra coil”, using the best method he had developed for detecting resonance (see 13 November). This result, which differs appreciably from the others, is not mentioned November 26th.
The remark closing this entry suggests the possibility of systematic error in the determination of resonance, and Tesla emphasizes that it has to be checked.
November 24
He applies the resonant method in order to check previously obtained values for inductances in the primary circuit (oscillator circuit) by method of current, voltage and frequency (please see Oct. 30). He changes the elements in the oscillator circuit so as to obtain the unchanged multiplication of inductance with capacitance. He described the same procedure on Oct. 21 and he performed some measurements, but without calculations. This time he performed measurements and calculations, but only for one combination of CpLp. He made comparison with the results obtained from the table attached to Nov. 8 by application of linear interpolation. Probably satisfied with the match, he did not continue further checking.
