. Electricity simplified. The practice and theory of electricity ... e also formed with all their characteristics. Thereis absolutely no difference between a permanent andcurrent-formed or electromagnet, except that thelatter may be made much stronger than a permanentone. These facts give the basis for the famous Ampereantheory of magnetism, devised by Andre Marie Ampere,the French scientist, from whom the practical unitof electric current-intensity is named. A permanent magnet is supposed to be a locusaround which electric currents are perpetually circu- 88 ELECTRICITY SIMPLIFIED. lating in t
. Electricity simplified. The practice and theory of electricity ... e also formed with all their characteristics. Thereis absolutely no difference between a permanent andcurrent-formed or electromagnet, except that thelatter may be made much stronger than a permanentone. These facts give the basis for the famous Ampereantheory of magnetism, devised by Andre Marie Ampere,the French scientist, from whom the practical unitof electric current-intensity is named. A permanent magnet is supposed to be a locusaround which electric currents are perpetually circu- 88 ELECTRICITY SIMPLIFIED. lating in the direction of the hands of a clock if onefaces the south pole or negative end. As a perma-nent magnet is not a seat of energy but of force, onlythe currents may be supposed to virtually consist ofan aggregation of molecular whirls in circuits of noresistance, and of molecular size, exactly as in linesof force in the air or any medium. Thus the cutshows at A the north pole and at B the south j:>oleof a magnet, and a b and c represent the minuteactive Fig. 20.—North and South Poles of a Magnet to Illustrate AmperesTheory. Two currents going in the same direction tend toplace themselves parallel. The earths polarity bythe Amperean theory is accounted for by assuming itto be girdled by electric currents approximately inplanes parallel to the equator, and going from east towest, opposite in direction to those encircling a mag-net whose north pole is pointing north. The ten-dency of the nearer portions of the two sets of circu- TERRESTRIAL MAGNETISM. 89 lar currents, one around the earth, the other aroundthe magnet, to coincide in direction, and to be par-allel, causes the magnet to point north and earth currents may involve the expenditure ofenergy, and probably do. Poor conductor as the sur-face of the earth may be, its interior may be better;and .in any case the great volume of the earth wouldcompensate for its normally high resistance. As amber was the
Size: 1769px × 1412px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, bookidel, booksubjectelectricity
