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Nikola Tesla Books

Books written by or about Nikola Tesla

Nikola Tesla: Colorado Springs Notes, 1899-1900 Page 183

September 8-11, 1899

Data for calculating inductance

diameter of coil d = 10 5/16" = 10.3125" = 26.19 cm.

$! {S = {{\pi \over 4} d^{2}} = {0.7854 \times 685.9} = 538.7} $! cm. sq. N = 550

l = 41.25" = 104.77 cm. N2 = 302,500

$! {L = {{4 \pi \over l} N^{2} \, S} = {{12.5664 \times 302,500 \times 538.7} \over 104.77} = 12.5664 \times 302,500 \times 5.14} $!

L = 19,538,800 cm. or 0.019539 henry approx.

following readings to measure the inductance were taken:

E I ω R average of three readings practically the same.
117 6.2 880 9.586

From these data

$! {{E \over I} = {117 \over 6.2}} $! = 19 approx.$! {\left(E \over I\right)^{2} = 361} $!   $! {R^{2} = 91.89} $!

$! {{\left(E \over I\right)^{2} - R^{2} = 269.11}} $!

$! {L = {\sqrt{269.11} \over 880} = {16.41 \over 880}} $! or

L = 0.01865 henry = 18,650,000 cm.

Colorado Springs

Sept. 11, 1899

Experiments were continued with apparatus before described and the effects outside at a distance investigated, the chief object being to establish nodal points on earth’s surface. The transmitting apparatus was one giving more rapid vibrations and was improvised as indicated in the left sketch.

The apparatus for investigation comprised the ten” drum, before referred to, wound with 395 turns wire No. 18 B. & S. and to increase magnifying factor another layer was wound on top, thus doubling the section. It was found that the scheme of double windings is not a good one because the e.m.f. in both wires are apt to be unequal and it is more difficult to make adjustment. The connections of apparatus were as indicated in the right sketch.

183

September 11

Tesla probably thought that he would more easily detect standing waves in the vicinity of the laboratory if the wavelength was shorter. He assumed that the ball-cable system would produce waves which could be registered by the receiver. However, although he measured the electromagnetic field up to a mile away, he probably did not find the expected variation, and could only conclude that electrical disturbances were registered.


September 11

He continued the experiments started two days ago with the intention of finding the nodes in the ground waves. He adjusted the oscillator to produce waves of somewhat higher frequencies than common ones, probably with the intention to get nodes of "standing" waves in the ground closer to the laboratory. The electromagnetic field he measures with the apparatus in Fig. 2, very slightly changed with relation to the previous one (please see Sept. 5, Fig. 3). Although he registered a signal at one mile distance from the laboratory, he does not mention how the signal varied with regard to distance.

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.