Various Tesla book cover images

Nikola Tesla Books

Books written by or about Nikola Tesla

Suppose an ideal system of this kind excited in the manner described, so that capacity on the free end is charged each time as the current alternates to a potential P. Then, since as before stated, the system in experiment illustrated was vibrating about 93,000 times per second, the total energy set in movement in the system would be

2 x 93,000 x $! {{P^{2} \times 145.8} \over {2 \times 9 \times 10^{11}}} $! watts.

Let it be further assumed that 1% of the total energy set in movement is frittered down in the lamps and that the number of these were 60, as might have been the case in the presently described experiment. Suppose each lamp to take 50 watts, the total energy consumed in the lamps would be 3000 watts hence, under the above assumptions, the total energy set in movement in the excited system would have to be 100 times this amount or 300,000 watts. To satisfy this condition we would have

2 x 93,000 x $! {{P^{2} \times 145.8} \over {2 \times 9 \times 10^{11}}} $! = 300,000


P2 = $! {{54 \times 10^{13}} \over {186 \times 145.8}} $! = $! {10^{12} \times {540 \over {186 \times 145.8}}} $! or P = $! {10^{6} \sqrt{540 \over {186 \times 145.8}}} $! =
= $! {10^{6} \sqrt{540 \over 27,118.8}} $! = $! {10^{6} \sqrt{0.02}} $! approx. or = $! {10^{6} \sqrt{2 \over 100}} $! = $! {10^{5} \sqrt{2}} $! =

= 105 x 1.414 or P = 141,400 volts.

Not very much, as will be seen, for such a pressure is extremely small with apparatus of the kind used here. Taking P roughly as 140,000 volts and assuming that the ground plate be at such a distance that only 1000 volts are impressed upon the same then the magnifying factor would have to be only 140. Of course, this is merely an example to support the above statement that considerable energy may in this way, and by such apparatus, be conveyed to a distant circuit which is connected to the ground at only one point directly or, if desired, through a condenser.

In another photograph, marked Plate XXIII., taken with same apparatus a similar experiment is illustrated. Here the extra coil as indicated in the diagram above is connected directly through the wire w to the ground plate and another coil designated in the diagram as “secondary” is placed in inductive relation to the extra coil excited in the same manner as in experiment before described, and a lamp is lighted by the currents generated in this “secondary”. Only one lamp was used as it was the object of the photograph merely to illustrate a novel experiment, but with reference to the above it will be understood that as many as 60 lamps, or nearly so, might have been lighted with the apparatus used in this manner. All the particulars were practically the same as before. The “secondary” had four turns, the excitation of the extra coil being reduced so that the lamp was somewhat above normal candle power. In this, as well as in the preceding experiment, the switch on the Westinghouse high tension transformer was thrown in and out


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.

January 2

Tesla gave his observations on 22 pages. On them he described eleven photographs. The explanation along with photograph No. 22 about energy transmission from excitation of the primary circuit to "additional coil" over the earth surface is similar to the one from 1893(6). Otherwise the experiment to which the photograph is related was performed for the purpose of oscillator power estimate on the basis of thermal effects of high frequency current.

That which Tesla calls "total energy placed in motion" would correspond to the total energy which is supplied to a capacitor per second (i.e. power) if energy ½CV2 is supplied during the duration of one half of the period. 

It could be shown that the active power which is spent in the circuit is considerably smaller than this power, and opposite, proportionally to the quality factor of the oscillating circuit. On several following photographs, the movable resonant coil with connected bulbs is photographed which is supplied by transmitted high frequency energy. One terminal of this coil is connected to the ground, and the other is open ended or a short piece of wire is connected to it. Bulbs are coupled by means of the auxiliary secondary coil inductively with the secondary coil. The data was not given on the distance of resonant coil from the oscillator coil. Tesla's comment on photograph No. 27 illustrates the interest on the question of electrical lightning, though he worked on this for more than ten years. One earlier discovery on gas elimination and not only filament, when working with high frequency currents is again proven(5).

On photograph No. 28 the bulb is connected in series with a terminal capacitance load. In the calculations "total energy placed in movement" is not taken when it was assumed that the electrostatic energy ½CV2 is spent in the bulb during one half of the period. A similar comment is valid for photograph No. 29.

Tesla mentioned several times that the main transmission from the exciting to the excited circuit is done via the ground. The proof for this statement he found in the experiment illustrated by photograph No. 30. He concluded that the induced voltage in the excited circuit is significantly reduced when the ground connection is disconnected. Photograph No. 31 is an X-ray photograph of a finger. The comments on this experiment are an illustration of Tesla's interest in the radiation field which was mentioned earlier (please see comment on June 6, 1899).


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.