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Nikola Tesla Books

Books written by or about Nikola Tesla

Nikola Tesla: Colorado Springs Notes, 1899-1900 Page 272

November 9, 1899

For coil wound with No. 6 wire:

E.m.f. across two primary turns+coil all in series E.m.f. across two primaries in series alone Current ω
14.5 6.4 30.9 880
14.5 6.4 30.9 880
14.5 6.4 30.9 880

For coil with No. 2 wire:

E.m.f. across two primary turns+coil all in series E.m.f. across two primaries in series alone Current ω
13.5 8.2 40.1 880
13.5 8.2 40.1 880
13.5 8.2 40.1 880

This would give approximately inductances of coil No. 6 wire.

l = $! {14.5 \over 6.4} $! x 230,945 - 230,945 = $! {8.1 \over 6.4} $! x 230,945 = 292,290 cm,

Coil No. 6 wire

and for coil No. 2 wire

l1 = $! {13.5 \over 8.2} $! x 230,945 - 230,945 = $! {5.3 \over 8.2} $! x 230,945 = 149,340 cm,

Coil No. 2 wire

These figures were first utilized then separate readings were taken. All the particulars of these coils and the measured and calculated values are as follows:

Coil wound with No. 6 wire:
length of wound part 38.75" = 98.425 cm, drum 5" = 12.7 cm. 129 turns

Thickness of wire with insulation $! {98.425 \over 129} $! cm. Thickness of bare wire = 0.162" = 0.41148 cm.

Thickness of two insulations $! {98.425 \over 129} $! – 0.41148 = 0.763 – 0.4115 = 0.3515 cm. This is to be added to the core 12.7 cm diam. making total diam. 13.0515 cm.

To calculate inductance we have therefore the following data:

d = 13.0515 cm, l1 = 98.425 cm, N = 129, N2 = 16641, S = $! { \pi \over 4} $! d2 = 133.786 cm.sq.

This gives l = $! {12.5664 \over 98.425} $! x 16,641 x 133.786 = 284,247 cm.

Now the readings to estimate from were:

e.m.f. Current ω R calculated approx. 180 feet wire 2535 ft. per ohm
13.3 49.1 880 0.071 ohm
13.3 49.1 880
13.3 49.1 880
$! {{E \over I} = 0.271} $!
$! {{\left({E \over I}\right)^{2}} = 0.073441} $!
$! {{R^{2} = 0.00504} \over {\left({E \over I}\right)^{2} - R^{2} = 0.0684}} $!

272

Source:
by Professor Aleksandar Marinčić

November 9

The measurements of mutual inductance in terms of the inductance of the primary when the secondary is open and short circuited are noteworthy. They were made at constant current and frequency, simplifying the calculation.

To reduce the oscillator frequency, in some cases Tesla used two special coils which he refers to only by wire gauge number. He compares the calculated and measured values for these coils. The values measured by the voltage ratio method are about 2% less than those found from voltage, current and frequency. The calculated values are lower than either. Correction of the measured values as described in the commentary to 26 October does not make much difference (about - 5%) because the D/l ratio is relatively small.

Source:
by Professor Aleksandar Marinčić

November 9

He performs the interesting measurements of the mutual inductance on the basis of the primary inductance when the secondary is open, and in short circuit. He measured inductances at constant current and frequency so the calculation procedure is simplified. The obtained mutual inductance he compared with the inductance determined previously by means of induced voltage under no load conditions. Tesla thinks that the difference originates from the influence of the secondary on the primary when the secondary is open. In some cases for the purpose of oscillator operating frequency reduction Tesla used two separate coils which he did not name but designated by numbers. He compared the calculated and measured values for these coils. The measured value on the basis of voltage the ratio method amounts to approximately 2% less than values measured on the basis of voltage, current and frequency. The calculated values are smaller in both cases. The correction of measured values according to comment of Oct. 26 is not large (approximately 5%) because the ratio D/1 is relatively small.

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.