The Science record; a compendium of scientific progress and discovery (1874) (14595634098)

Identifier: sciencerecordcom1874beac (find matches)

Title: The Science record; a compendium of scientific progress and discovery

Year: 1872 (1870s)

Authors: Beach, Alfred Ely, 1826-1896

Subjects: Technology Industrial arts

Publisher: New York, Munn

Contributing Library: Smithsonian Libraries

Digitizing Sponsor: Smithsonian Libraries

Text Appearing Before Image:

, it will produce a south pole in the iron bar, which willgradually be displaced from one end of it to the other, fol-lowing the motion of the bar magnet. The result is acontinuous induced current in the surrounding wire. If,now, the soft iron bar be made into a ring A, and placed be-tween the poles of a horse-shoe magnet D, these poleswill of course induce currents in opposite directions, neu-tralizing each other at two points of the ring, midwaybetween the poles, exactly (according to Mr. Crookes) asif we had two batteries connected in opposition by joiningtheir similar poles. On revolving the iron ring on the ELECTRICITY, LIGHT, HEAT, SOUND. 207 journals E, a continuous current is developed, as in thecase of a straight bar, but in opposite directions, becausehere we have to do with both poles of the exciting mag-net. Both these currents will continually neutralize eachother at the two mean points. To utilize them, all that isnecessary is to connect conducting wires to the insulated

Text Appearing After Image:

GRAMMES NEW ELECTRIC-LIGHT MACHINE. wire at the mean points, and they will flow along thesewires instead of neutralizing each other; just as in thetwo batteries above, connecting a disk F with each pointof contact of the similar poles, will cause the force of thebatteries to flow through the conducting wires quantity-wise. M. Gramme accomplishes this in the followingmanner: 208 SCIENCE RECORD. If the wire wound upon the ring is very thick and thereis but a single layer of it, it is sufficient to remove the in-sulating covering at some point which, in its revolution,is made to touch fixed metallic conductors F, situated atthe neutral points. If, however, many layers of fine wireare used, the following device is adopted : The wire isdivided into sections of, say, 300 turns each, there beingno break, however, in the wire on passing from one sec-tion to another. Each section has its wire exposed atonepoint, and to this point is soldered a solid bar of brass B,capable of considerable wear

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1874

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