Various Tesla book cover images

Nikola Tesla Books

Books written by or about Nikola Tesla

Nikola Tesla: Colorado Springs Notes, 1899-1900 Page 343

January 1, 1900

Colorado Springs

Jan. 1, 1900

Photographs taken Dec. 22. and 23; with Mr. Alley from Dec. 17 to Dec. 31, 1899 and particulars about the same:

XV. Shows an incandescent lamp 16 c.p., 100 V placed out on the field with two wires leading to it. Snow on the ground. The lamp is lighted.

XVI. Illustrates the same with three lamps 16 c.p., 100 V placed on the snow and lighted. The lamps are connected in multiple arc.

XVII. Photograph showing once more the same with three lamps as before, the lamps being placed on black cloth to improve effect. These photographs were taken under the following conditions:

A cord of section equal to that of wire No. 10 was laid on the field in the form of a square of 62' 5" = 749" = 1902.5 cm side, the center of the square being from the center of the primary loop of the oscillator in the laboratory a little over 60 feet = 720" = 1830 cm. The ends of the square were connected to two small condensers joined in multiple and each having a little less than 1/20 mfd. Neglecting capacity of the cord against that of the condensers the total effective capacity of this system was, with fair approximation 1/10 mfd, or 90,000 cm. The inductance of the square, taking it as consisting of two pairs of parallel wires, was

Ls = 2 x 2 l(loge$! {d^{2} \over r r'} $! + 1/2).

In the present instance

l = 1902.5 cm,   d = 1902.5 cm,   r = r' = 0.254 cm.

$! {d^{2} \over rr'} $! = $! {d^{2} \over r^{2}} $! = $! {\left({d \over r}\right)^{2}} $! = $! {\left({1902.5 \over 0.254}\right)^{2}} $! = (7500)2 and Ls = 4 x 1902.5 x

x (loge 75002 + 1/2) = 7610 x (17.825 + 0.5 ) = 7610 x 18.325 = 761 x 183.25

log 7500 = 3.875061 Ls = 139,450 cm, or $! {13,945 \over 10^{8}} $! henry

2 log 7500 = 7.750122
2 loge 7500 = 7.75 x 2.3 = 17.825 approx.

From the foregoing we have for the period of the secondary system:

Ts = $! {{2 \pi \over 10^{3}} \sqrt{0.1 \times {13,945 \over 10^{8}}}} $! = $! {{2 \pi \over 10^{7}} \sqrt{1394.5}} $! = $! {{2 \pi \times 37.34} \over 10^{7}} $! = $! {234.5 \over 10^{7}} $!

and this would give n = 42,640 approx, per second.

Now resonance in this circuit was obtained with all jars being connected as usual and two primary turns in multiple, there being besides in the primary circuit 18 1/2 turns of the regulating coil. This gives approximately the capacity of primary or exciting circuit $! {{8 \times 36} \over 2} $! jars = 144 jars or bottles = 0.0009 x 144 = 0.1296 mfd. Neglecting for the moment

343

Source:
by Professor Aleksandar Marinčić

January 1

Photograph XVII shows lamps connected into a resonant circuit consisting of one square turn. According to the data Tesla gives, one side of the square was about 1.3 m from the secondary coil of the oscillator. The capacity of the oscillatory circuit consisted of two condensers in parallel. The lamps are paralleled.

Tesla calculates the inductance of the square turn from the formula for the inductance of two parallel conductors, as if there were two such pairs connected in series. The formula for a square coil (Fleming, p. 155),

L = 8l(In $!{d \over r}$! - 0.774)

yields a value 12.6% less than Tesla found. The calculated resonant frequency is therefore somewhat higher than it should be, so that the inductance of the oscillator primary, as Tesla calculates it, is still less. In fact, because of the tight coupling of the secondary the oscillator must have been producing a complex spectrum, probably with its strongest component at the resonant frequency of the oscillatory circuit of the square coil.

In connection with photographs XVIII - XXI showing the secondary producing intense discharges, Tesla makes an interesting remark about signalling over great distances. Comparing this with other induction apparatuses he had constructed, he concludes that one could expect signals to be picked up at distances of a thousand miles or more, even on the Earth's surface. The diary does not mention any measurements at great distances, but in an article(41) he published soon after finishing work at Colorado Springs he states that he observed effects at a distance of about 600 miles.

Source:
by Professor Aleksandar Marinčić

January 1

On photograph XVII, bulbs are shown connected to the resonant circuit made of one turn rectangular in shape. According to data mentioned the square edge is 1.3 meters away from the oscillator secondary coil. The capacitance of the oscillating circuit consists of two capacitors connected in parallel. The bulbs are connected in parallel. The square turn inductance Tesla calculated according to an equation for two parallel conductors' inductance as those are two parallel conductors pairs connected in series. When the calculation is done as per equation for a square coil (Fleming, p. 155):

L = 81 (ln $! {d \over r} $! - 0.774)

The value obtained is 12.6% smaller than the one found in the notes. The calculated value of a square coil circuit resonant frequency is due to that somewhat higher, and therefore the inductance of the oscillator primary coil calculated as Tesla does it is even smaller. In fact, due to the existence of a very good coupled secondary the oscillator has complicated the oscillating spectrum with probably the strongest component in the frequency of the oscillating circuit with a square coil.

Related to four secondary coil photographs with extensive discharge the remark about energy transmission over a distance is interesting.

Tesla concluded on the basis of comparisons with achieved induction apparatus that the signal registration could be performed at the distance of 1000 or more miles, even over the earth globe surface. There is no data in the notes about measurements over longer distances, and in article(41) written immediately after the finish of the work at Colorado Springs, he says that he observed the effects at a distance of approximately 600 miles.

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.