Nikola Tesla Books
Books written by or about Nikola Tesla
to the primary vibration when the capacity in the primary or exciting circuit was 1 2/3 tanks or 60 bottles on each side, or 30 bottles total, that is, 30 x 0.0009 = 0.027 mfd, total.
The vibrations were impressed on the ground plate by the oscillator with normal connection, that is, two primary cables in multiple or one primary turn, the approximate inductance of which was 56,400 cm or, say, 56,000 cm, which is close enough for the present consideration. This inductance may have been modified by the secondary, but the effect of the latter must have been very slight as, with the capacity used, it was "out of tune" and the current through it was necessarily very small. Taking then the inductance of the primary exciting circuit at 56,000 cm, the period of this circuit was
Tp = !$ {{2 \pi \over 10^{3}} \sqrt{0.027 \times {56 \over 10^{6}}}} !$.
Now calling Cs the "ideal" capacity of the excited circuit, the period of the same was
Ts = !$ {{2 \pi \over 10^{3}} \sqrt{{185 \over 10^{4}} \times C_{s}}} !$ and equating we have Cs = !$ {{10^{4} \over 185} \times 0.027 \times {56 \over 10^{6}}} !$ = !$ {{56 \times 0.027} \over {185 \times 10^{2}}} !$ mfd,
or Cs = !$ {{9 \times 10^{5} \times 56 \times 0.027} \over {185 \times 10^{2}}} !$ = !$ {{243 \times 56} \over 185} !$ = 75.2 cm, approx. From above
Tp = !$ {{2 \pi 10^{3}} \sqrt{0.027 \times {56 \over 10^{6}}}} !$ = !$ {{2 \pi \over 10^{3}} \sqrt{1.512}} !$ = !$ {{6.28 \over 10^{6}} \times 1.23} !$ = !$ {7.7244 \over 10^{6}} !$
and n = 129,500 per second nearly.
The theoretical wave length would thus be λ = !$ {186,000 \over 130,000} !$ = !$ {186 \over 130} !$ = 1.43 miles approx.
or !$ {λ \over 4} !$ = !$ {1.43 \over 4} !$ = 0.3575 miles or 0.3575 x 5280 = 1888 feet = !$ {λ \over 4} !$.
The actual length of wire in the experiment was: 274 turns of the coil, each 79.29" = 1810 feet + one piece of wire 304 feet + one piece of wire 84 feet = 1810 + 304 + 84 = 2198 feet or nearly 15% more than the theoretical value. The fact is, the adjustment for resonance was not quite close as the lamp lighted could not withstand the current by closer adjustment. Two of these lamps were broken. The energy transmitted through the ground to the coil was, of course, small in this instance, since only a small part of the available primary capacity was used, that is, !$ {1.66 \over 8} !$ of the available capacity and the current of the supply transformers was reduced as far as practicable. If a coil especially adapted for the full output of the oscillator would have been used it would have been practicable to transmit many times the amount of energy needed for lighting the lamp. The lamps used in this experiment were special ones each taking, under the conditions of the experiment, perhaps 10 watts or nearly so. Assuming again a circuit under ideal conditions with the capacity of 75.2 cm on the free end of a coil without distributed capacity, and calling the potential to which this capacity would be charged P, the total energy set
23
Hertz, H.R. UNTERSUCHUNGEN UBER DIE AUSBREITUNG DER ELEKTRISCHEN KRAFT, dritte auflage, Leipzig, 1914, Johann Ambrosius Barth.
The explanation to Photograph XXII concerning the transmission of power from the excited primary circuit to the "extra coil" via the earth is similar to that he gave in 1893(6). The experiment to which the photograph refers was made with the aim of estimating the power of the oscillator from the thermal effect of the HF current. What Tesla calls the "total energy set in movement" would correspond to the total energy transferred to condenser in the secondary (i.e. the power) if an energy of !${1 \over 2}!$ CV2 is transferred in each half-cycle. It can be shown that the active power dissipated in the circuit is much less than this and is inversely proportional to the Q-factor of the oscillating circuit.
