Various Tesla book cover images

Nikola Tesla Books

Books written by or about Nikola Tesla

Nikola Tesla: Colorado Springs Notes, 1899-1900 Page 359

January 2, 1900

total inductance of the exciting circuit was 58,684 cm, or, with fair approximation, 59,000 cm = 59/106 henry.

These data give

T = !$ {{2 \pi \over 10^{3}} \sqrt{0.0486 \times {59 \over 10^{6}}}} !$ = !$ {{2 \pi \over 10^{6}} \sqrt{2.8674}} !$ = !$ {{6.28 \over 10^{6}} \times 1.7} !$ = !$ {10.676 \over 10^{6}} !$

and n = 93,700 approx. and 588,000 = p nearly.

If we assume, as in previous cases, that one percent of the total energy of the vibrating system is used up in the lamp in unrecoverable form, the energy of the system would then be 100 wats per each watt used in the lamp, or taking the lamp at 16 c.p. consuming, say, 50 watts the energy of the system would have to be 5000 watts. From this we get the potential P on the free end of the coil approximately by equating:

5000 = !$ {{c \over {9 \times 10^{11}}} \times {{P^{2} \times 93,700 \times 2} \over 2}} !$

Here c would be the capacity of the lamp or other object, in centimeters, and taken in the same way as before explained. In previous measurements by resonance analysis the capacity of such a lamp was found to be only 1 cm, approximately. Taking this value for c we have:

P2 = !$ {{5 \times 10^{3} \times 9 \times 10^{11}} \over {937 \times 10^{2}}} !$ = !$ {{45 \times 10^{12}} \over 937} !$

and

P = !$ {10^{6} \sqrt{45 \over 937}} !$ = !$ {10^{6} \sqrt{0.048}} !$ = !$ {10^{6} \times 0.22} !$

or = 220,000 volts = P. This shows that P would be rather large on the assumption of but 1% frictional work in the lamp. In reality, as I know by experience, there will be generally much more energy, of the total energy of the system, used up in the lamp so that the potential P will be found in practice much smaller. But it is to be stated that owing to the small capacity of the lamp it will be relatively very high. By providing capacity in any way, so as to enable the lamp to take more energy, the potential required may be reduced at will.

This will be apparent from another photograph which is marked XXVIII. In this instance the same connections were used as before, only the free terminal of the lamp was connected by a wire to the structure of iron pipes above. The wire can be scarcely distinguished. In this experiment resonance with the exciting circuit was obtained with 6 tanks on each side, this would mean a capacity of three tanks or 108 bottles = 108 x 0.0009 = 0.0972 mfd.

The inductance of the exciting circuit comprised a primary

359

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.