Various Tesla book cover images

Nikola Tesla Books

Books written by or about Nikola Tesla

Nikola Tesla: Colorado Springs Notes, 1899-1900 Page 356

January 2, 1900

in movement in the excited system would be 2 x 129,500 x !$ {{P^{2} \times 75.2} \over {2 \times 9 \times 10^{11}}} !$ watts.

If we assume that, as before, 1% of the total energy of the system is frittered down in the lamp we would have, in conformity with what was stated before for determining P, the equation

!$ {2 \times 129,500 \times {{P^{2} \times 75.2} \over {2 \times 9 \times 10^{11}}}} !$ = 1000 or P2 = !$ {{18 \times 10^{11}} \over 259} !$

or

P = !$ {10^{5} \sqrt{180 \over 259}} !$ = !$ {10^{5} \sqrt{0.695}} !$ = !$ {10^{5} \times 0.834} !$

or 83,400 V nearly, which is a small e.m.f. The length of wire in excited circuit was as before stated 2198 feet; the wire being No. 10, with a resistance of 1 ohm per one thousand feet, the resistance of the circuit was about 2.2 ohm. From above p = 2!$ \pi !$n was = 6.28 x 129,500 = 813,260 or, say, 813,000 = p. The inductance being, as shown, !$ {185 \over 10^{4}} !$ henry, the magnifying factor in the coil was !$ {{{185 \over 10^{4}} \times 813 \times 10^{3}} \over 2.2} !$ = 6840 nearly. The lamp was one with a very short filament and its resistance may have been possibly 6 ohms. Thus with the lamp comprised the magnifying factor was still very considerable, that is, !$ {{185 \times 813} \over 82} !$ = 1830 or nearly so. Taking it at 1800 we see that it was necessary, under the conditions assumed, to impress upon the ground plate, or near portions of the ground an electromotive force of only !$ {83,400 \over 1800} !$ = !$ {834 \over 18} !$ = 52 volts or nearly so! This seems very little indeed, it can be scarcely believed, but the figures seem to be not far from truth. These remarks refer particularly to the experiment illustrated on the plate marked XXIV. in which the connections were the same as in the diagram shown when discussing Plate XXII., the lamp or lamps being in series with the excited coil or system.

In the experiments illustrated in the Plates marked XXV. and XXVI., the connections were schematically the same as in diagram shown a propos Plate XXIII. and the vibrations and other particulars were practically the same as in experiment shown in Plate XXIV. Just described. It is to be stated that when a secondary circuit is used, as in experiments described under XXIII., XXV. and XXVI., in connection with the excited coil, this secondary should for maximum effect be placed near the lower end of the coil; the exact position may be determined by experiment or approximately calculated. Namely, if the coil which is excited were devoid of capacity and the necessary capacity were all on the upper or free end of the coil, then the secondary circuit should, for maximum effect, be just at the center of the coil. But in the experiment as shown, the capacity is distributed and the current is strongest in the first or lowest turn, diminishing towards the top of the coil in each turn. The resultant maximum effect is thus always found near the lower end of the coil, but not quite at the end, since the upper turns also effect the secondary circuit, though proportionately less than the lower ones. The calculation of the maximum position of the secondary is complicated by the fact that generally neither the capacity nor the potential is uniformly distributed, the distribution being greatly varied by very slight irregularities in the dimension of the individual turns or their position, or the position

356

Source:
by Professor Aleksandar Marinčić

January 2

In this entry of 21 pages (the longest in the Notes) Tesla describes 11 photographs.

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.

The next few photographs show a movable coil which powers light bulbs by means of the high-frequency power which it picks up. One end of the coil is grounded, the other free or just connected to a short piece of wire. The bulbs are inductively coupled to the resonant coil via the auxiliary secondary. Tesla gives no data about the distance of the resonant coil from the oscillator coil.

Tesla's commentary on photograph XXVIII illustrates that he still retained a lively interest in the problem of electric lighting, even after a period of over ten years. His earlier discovery of the luminescence of the gas and not only the filament with HF currents was here again confirmed(5).

In photograph XXVIII the bulb is connected in series with the terminal capacitive load. In the calculation Tesla does not use the "total energy set in movement" but assumes that 1/2 CV2 of electrostatic energy is consumed in the bulb in each half-cycle. A similar comment applies to photograph XXIV.

Several times Tesla remarks that the principle energy transfer from the oscillating to the receiving coil takes place via the earth. He finds confirmation for this in the experiment described on p. 363 (photograph XXX). He found that the voltage induced in the receiving coil was greatly reduced if the ground connection was broken. It may be that such experiments led him to the conclusion that "transmission" through the earth was a more efficient method of wireless transmission of power than the "inductive method".

Photograph XXXI is an X-ray picture of a finger. Tesla's comments on this experiment illustrate his interest in this type of radiation, already referred to (see the commentary to 6 June 1899).

Contents

Introduction
June 1 - 30
July 1 - 31
August 1 - 31
September 1 - 30
October 1 - 31
November 1 - 30
December 1 - 31
January 1 - 7
Commentaries

Appendices: I, II

Images

Glossary

Lowercase tau - an irrational constant defined as the ratio of the circumference of a circle to its radius, equal to the radian measure of a full turn; approximately 6.283185307 (equal to 2π, or twice the value of π).
A natural rubber material obtained from Palaquium trees, native to South-east Asia. Gutta-percha made possible practical submarine telegraph cables because it was both waterproof and resistant to seawater as well as being thermoplastic. Gutta-percha's use as an electrical insulator was first suggested by Michael Faraday.
The Habirshaw Electric Cable Company, founded in 1886 by William M. Habirshaw in New York City, New York.
The Brown & Sharpe (B & S) Gauge, also known as the American Wire Gauge (AWG), is the American standard for making/ordering metal sheet and wire sizes.
A traditional general-purpose dry cell battery. Invented by the French engineer Georges Leclanché in 1866.
Refers to Manitou Springs, a small town just six miles west of Colorado Springs, and during Tesla's time there, producer of world-renown bottled water from its natural springs.
A French mineral water bottler.
Lowercase delta letter - used to denote: A change in the value of a variable in calculus. A functional derivative in functional calculus. An auxiliary function in calculus, used to rigorously define the limit or continuity of a given function.
America's oldest existing independent manufacturer of wire and cable, founded in 1878.
Lowercase lambda letter which, in physics and engineering, normally represents wavelength.
The lowercase omega letter, which represents angular velocity in physics.