. Electricity simplified. The practice and theory of electricity ... and viceversa. Again, if the earth is a magnet, lines of force shouldemanate from it, running from pole to pole, andfrom intermediate spots south of the magnetic equa-tor to points of equal potential north of the lines of force have been proved to exist and byinductive action like that exercised by the field mag-nets of a dynamo upon its rotating armature a cur-rent is readily produced from them. The simplerotation of a coil about an axis properly placed is allthat is necessary to produce a current. Such a coilis
. Electricity simplified. The practice and theory of electricity ... and viceversa. Again, if the earth is a magnet, lines of force shouldemanate from it, running from pole to pole, andfrom intermediate spots south of the magnetic equa-tor to points of equal potential north of the lines of force have been proved to exist and byinductive action like that exercised by the field mag-nets of a dynamo upon its rotating armature a cur-rent is readily produced from them. The simplerotation of a coil about an axis properly placed is allthat is necessary to produce a current. Such a coilis termed an earth coil and an example of one withgalvanometer in the circuit is shown in Fig. 22. The lines of force should vary in intensity fromthe magnetic equator toward the magnetic poles, anda given earth coil rotated at a fixed rate should givedifferent currents, those of greater intensity as it is MAGNETIC POLES OF THE EARTH. 91 nearer to the magnetic poles. This is the case infact, and is shown also in the varying directive powerof the earth upon a Fig. 22.—Earth Coil. On the earths surface matters would be simplifiedif the Amperean currents coincided with the parallelsof latitude. Then the true equator would mark theneutral line or magnetic equator, and the magneticpoles would coincide with the poles of is not the case, however. The Amperean earthcurrents are slightly irregular, so that the magnet orcompass needle in placing itself at right angles tothese currents will not, except at particular places,point north. Thus, the magnetic poles of the earth,determined by the intersection of verticals to theAmperean current lines, do not coincide with the 92 ELECTRICITY SIMPLIFIED. true poles. The irregularity also is iu a perpetualstate of change. The compass needle, in seeking the magnetic poles,also tends to leave the horizontal, or to dip/ show-ing that the poles in question have their locus belowthe surface of the earth. A magnet, it is known,
Size: 1966px × 1271px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, bookidel, booksubjectelectricity
