## Nikola Tesla Books

Books written by or about Nikola Tesla

# Nikola Tesla: Colorado Springs Notes, 1899-1900Page 124

July 31, 1899

if the condensers are properly designed. The virtue of condensers used in such a manner is well established and I think it resides in the fact that when they are used the charge does not distribute itself along the wire, but accumulates on the coatings of the condensers thus reducing the effect of mutual electrostatic induction of the adjacent or near positions of the wire, to a large extent, and reducing in this manner the amount of energy stored in the coil itself. It now remains to consider the capacity on the end of the secondary which is “free”. This capacity ought to be so large that it can take up all the current of the secondary at the frequency used. Or, to put it otherwise, it should be able to store all the energy the secondary is able to give. There is, however, another consideration which must be made in case the secondary is capable of free vibration, and that is that the capacity on the end should be so determined as to secure resonance with the primary. As regards this capacity there are then three relations to be borne in mind when deciding upon this and they are:

 $!i=Ec_{s}ω$! $!{c_{s}={i \over Eω}}$! . . . . . . . . . . . . . . . . . . . . . 1) E secondary e.m.f. ω " frequency Watts in secondary $!W = {c_{s} E^2 ω \over 2}$! or $!{c_{s} = {2W \over E^2 ω}}$! . . 2) Lp inductance in primary Cp capacity $!L_{p} \, C_{p} \, = \, c_{s} \, L_{s}$! or $!c_{s} \, = \, {L_{p} C_{p} \over L_{s}}$! . . . . . . . . . . . . . . . . 3) Ls inductance secondary

July 31

Tesla made the condensers for the primary circuit out of mineral water bottles filled with a saturated solution of rock salt, and standing them in a metal tank of the same solution, thus creating a condenser bank with one common plate. The other plates (the electrolyte in the bottles) could be connected in parallel as desired. The smallest capacity adjustment possible was equal to the capacity of one bottle.

After various tests of what voltage the glass dielectric of the bottles could stand, Tesla returned his attention to the secondary of the oscillator, in which rightly way the limiting factor for obtaining higher voltages. His analysis of the distributed capacity of the secondary is a good illustration of his inventiveness in a little known field and how he sought to reduce problems to a simple but mathematically and physically sufficiently accurate model. It must not be forgotten that these are Tesla's working notes, which is sufficient justification in itself for some of the hypotheses which the reader might otherwise rightly object to.

July 31

Tesla made the capacitors for primary circuit from mineral water bottles filled with a saturated solid salt solution. He then submerged several bottles in a metal tank filled with the same solution. By that method he obtained the capacitor groups with a common layer. Other layers (electrolyte in jars) could have been connected in parallel as desired. The least capacitance change of capacitor battery of this type amounted to exactly the capacitance of one jar. By performing the withstand tests on such capacitors at a frequency of 144 Hz he concluded that they could withstand even 30,000 volts when two series of them are connected in series. By so solving the capacitor problems in primary circuit, he returns again to the secondary circuit. In the secondary he hadn't yet solved the problem of coil distributed capacitance, in which he sees the main obstacle on the way of achievement of desirable high voltages. Tesla's analysis, somewhat strange for a reader of these days (sometimes even incorrect) as hosed on a limited number of facts, impressed with its breadth. Tesla deeply penetrates in physical processes, and attempts to understand what and how something happens. His experiments provide him with proofs for conclusions he came to on the basis of thinking and analysis of previous experiments.

By having a desire to design the secondary coil with minimal self-capacitance, and which will be able to operate at extraordinary high voltages, Tesla devoted his time, more than anybody else before him, to a study of coils. The results were not lacking (coil shapes, winding methods), but with all that Tesla was not satisfied. He thinks what would happen when he would add series capacitors, and what would happen if he could change the distance between windings, or the wire diameter, etc.

## 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 &amp; Sharpe (B &amp; 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&nbsp;angular velocity in physics.&nbsp;