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He could make quite an issue out of the need to determine the characteristic impedance of their sky. That might even be interesting, at that; would it be anywhere near 300 ohms here? But it seemed that stalling wasn't going to work. They'd given him what they expected him to need, and he'd have to be careful to need only what they expected, or they might just decide he wasn't Dave Hanson.
The trouble began, however, when the wire reached Cleveland, O., about 700 miles from New York. Upon making a test at Cleveland, I found the signals made a continuous black line upon the chemical paper. I then placed both ends of the wire to earth through 3,000 ohms resistance, and introduced a small auxiliary battery between the chemical paper and earth.
I have now to draw your attention to a new motor of my own invention, of the weight of 124 lb., which, at 1,550 revolutions, gives 31 amperes and 61.5 volts at terminals. The mechanical horse power is 1.37, and the coefficient 373. Ohms. Armature resistance 0.4 w. Field-magnet resistance 0.17 w. Insulation resistance 1,500,000 w.
The electromotive force is independent of the velocity, but diminishes as the moisture increases, and is about equal to 52,000 Daniell cells. The resistance when making 120 revolutions per minute is 2,810 million ohms. At 450 per minute, 646 million.
A movable contact arm that slides over and presses on the turns of wire is fixed to the knob on top of the rheostat. A rheostat that has a resistance of 6 ohms and a current carrying capacity of 1.5 amperes which can be mounted on a panel board is the right kind to use. Assembling the Parts.
Supported in this wooden frame marked C is a spiral similar in construction to the one marked B, but in this case the copper wire is 0.044 inch in diameter, silk-covered, and consists of 365 turns, with a total length of 605 yards; its resistance is 10.2 ohms, the whole is inclosed between two thick sheets of card paper.
That is, by dividing the resistance of the circuit in ohms, by the electromotive force of the current you will get the amperes flowing in the circuit. Finally if you know what the resistance of the circuit is in ohms and the current is in amperes then you can find what the electromotive force is in volts since: Ohms x Amperes = Volts, or R x I = E
Extending from a point, o, in the main line, near the transmitting station, to the earth at G, is a branch conductor, l, containing an adjustable artificial resistance, R. A similar conductor, ll, extends from a point, o', near the receiving terminal of the line, L, to the conductor, 3, in which an artificial resistance, R', is also included, this resistance being preferably approximately equal to the resistance, R. The proportions of the resistance of the main line and the artificial resistances which I prefer to employ may be approximately indicated as follows: Assuming the resistance of the main line to be 900 ohms, the resistance, R, and R', should be each about 3,000 ohms.
The resistance of such a filament hot is about 200 ohms, and to produce a good light from it the battery or dynamo ought to give an electromotive force of at least 100 volts. Few voltaic cells or accumulators have an electromotive force of more than 2 volts, therefore we require a battery of 50 cells joined in series, each cell giving 2 volts, and the whole set 100 volts.
The droning voice of the professor continued to wind itself slowly round and round the coils it spoke of, doubling, trebling, quadrupling its somnolent energy as the coil multiplied its ohms of resistance. Moynihan's voice called from behind in echo to a distant bell: Closing time, gents! The entrance hall was crowded and loud with talk.
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