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Updated: May 14, 2025
But without any conductor no current could be delivered, and therefore there must be some resistance, and so the full power of the Electro-motive force can never be delivered by the Current. The amount that will be delivered is the original power of the Electro-motive force divided by the Resistance.
Lipmann further showed the reverse effect, that if a piece of mercury be forcibly pressed, so as to alter the convexity of its surface, such as by bringing it into a narrower part of the tube, then there is an electro-motive force produced.
"In Fig 1 there is seen, at e, gutta-percha separating the zinc from the carbon at the base. "Under such conditions, we obtain a powerful couple that possesses an electro-motive power of 1.5 to 1.8 volts, according to the concentration of the exciting liquid. The internal resistance is extremely feeble.
It occurred to me, and no doubt it did to Breguet also, that if we speak either against the surface of the glass tube, and caused the tube to vibrate, or if the mercury were caused to vibrate in the manner I have shown, we ought to be able to introduce a varying current in the wires which might have sufficient electro-motive force to produce audible speech in a Bell telephone.
But the electro-motive force, ascribed by Volta to the metals, when in contact, is a force which, as long as a free course is allowed to the electricity it sets in motion, is never expended, and continues to be excited with undiminished power in the production of a never-ceasing effect.
E. F. Fox might be produced by the gradual oxidation of mixed sulphides, and that veins containing bands of different metallic sulphides, bounded by continuing walls, and saturated with mineral waters, may constitute under some circumstances a large voltaic battery competent to produce electro-deposition of metals, and that the order of the deposit of these mineral lodes will be found to bear a definite relation to the order in which the sulphides rank in the table of their electro-motive power.
If a power generator by wireless transmission, without any metallic connection, can work one motor at a distance of, say, 1,000 miles, then it can also operate millions of similar possible motors situated at the same distance; and by far the greater part of its electro-motive force must be wasted in upward dispersion.
In our cities and towns where the current has only to go a short distance from the power house, the conductors are generally placed in cables underground and the maximum electro-motive force scarcely ever exceeds 11,000 volts.
"'Far I dipt beneath the surface, through the texture of the earth, Till my heart's triumphant musings dreamt the dream of that new birth, When the engineer's deep science through the mighty sphere shall probe, And the railway trains to Melbourne sweep the centre of the globe, And the electro-motive engine renders it no more absurd That a human being should be in two places like a bird.
The two major cables carry currents running in opposite directions, and as these currents are both caused to return along the third and smaller wire their electro-motive forces balance one another, with the result that the return wire needs only to carry a small difference-current.
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