Electrical Measurements and Other Advanced Primers of Electricity

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J.W. Johnston Company, limited, 1893 - Electric measurements - 429 pages
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Page 287 - A dynamo-electric machine is a machine for converting energy in the form of mechanical power into energy in tlie form of electric currents, or vice versa, by the operation of setting conductors (usually in the form of coils of copper wire) to rotate in a magnetic field, or by varying a magnetic field in the presence of conductors.
Page 252 - ... simple mode of vibration from them. It is possible, but unlikely ; for atoms, even when isolated, have a multitude of modes of vibration special to themselves, of which only a few are of practical use to us, and we do not know how to excite some without also the others. However, we do not at present even deal with individual atoms. We treat them crowded together in a compact mass, so that their modes of vibration are really infinite.
Page 252 - However, we do not at present even deal with individual atoms; we treat them crowded together in a compact mass, so that their modes of vibration are really infinite. We take a lump of matter, say a carbon filament or a piece of quicklime, and by raising its temperature we impress upon its atoms higher and higher modes of vibration, not transmuting the lower into the higher, but superposing the higher upon the lower, until at length we get such rates of vibration as our retina is constructed for,...
Page 251 - We want a certain range of oscillation, between 7000 and 4000 billion vibrations per second : no other is useful to us, because no other has any effect on our retina ; but we do not know how to produce vibrations of this rate. We can produce a definite vibration of one or two hundred or thousand per second ; in other words, we can excite a pure tone of definite pitch ; and we can command any desired range of such tones continuously by means of bellows and a keyboard. We can also (though the fact...

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