Lessons in practical electricity; principles, experiments, and arithmetical problems, an elementary text-book . al Representation of anAlternating Current. current and E. M. F. varied. Thisvariation in magnitude is represented in Fig. 311, which isconstructed similar to Fig. 310, but the current graduallyrises to its maximum value of 5 amperes, P to A, and asgradually diminishes again to zero, A to B, during the firstsecond, which may also represent one-half revolution of theloop. Corresponding with the second half revolution, the current graduallyrises from B, reach-ing its maximumnegative va
Lessons in practical electricity; principles, experiments, and arithmetical problems, an elementary text-book . al Representation of anAlternating Current. current and E. M. F. varied. Thisvariation in magnitude is represented in Fig. 311, which isconstructed similar to Fig. 310, but the current graduallyrises to its maximum value of 5 amperes, P to A, and asgradually diminishes again to zero, A to B, during the firstsecond, which may also represent one-half revolution of theloop. Corresponding with the second half revolution, the current graduallyrises from B, reach-ing its maximumnegative value at C(three-quarter rev-olution), and fall-ing again to zero atD, and so on. Inan alternating cur-rent dynamo thealternating current wave is not so abrupt as that depicted inFig. 311, but more truly represented by the undulatory curve,Fig. 312, which represents the same variations as at the end of one-half second the current reaches itsmaximum value, 5 amperes, represented to scale by the lineAG, while the value of the current at one-quarter second isequal to the line LK, or about 3 Fig. 312.—Graphical Representation of an Alter-nating Current. 342 PRACTICAL ELECTRICITY. 322. Magneto Alternator.—The E. M. F. of a dynamodepends upon, (a) The number of lines of force cut by the armature wires, (b) The number of cutting wires, (c) The speed at which the lines of force are cut. The E. M. F. of the single loop armature, Fig. 308, willtherefore be increased by winding it upon an iron core calledthe armature core, as in Fig. 313, which greatly increases thenumber of lines of force between the poles N and S, and alsoby winding a great many turns in the samedirection around this core. Fig. 313illustrates a Siemens shuttle armature,which is revolved between the poles of
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