CHAPTER XXXIII.

Method of Obtaining Direct From Alternating Currents.

This method consists in obtaining direct from alternatingcurrents, or in directing the waves of an alternating current so asto produce direct or substantially direct currents by developingor producing in the branches of a circuit including a source of al-ternating currents, either permanently or periodically, and byelectric, electro-magnetic, or magnetic agencies, manifestations ofenergy, or what may be termed active resistances of oppositeelectrical character, whereby the currents or current waves of op-posite sign will be diverted through different circuits, those ofone sign passing over one branch and those of opposite sign overthe other.

We may consider herein only the case of a circuit divided intotwo paths, inasmuch as any further subdivision involves merelyan extension of the general principle. Selecting, then, any cir-cuit through which is flowing an alternating current, Mr. Tesladivides such circuit at any desired point into two branches orpaths. In one of these paths he inserts some device to createan electromotive force counter to the waves or impulses of cur-rent of one sign and a similar device in the other branch whichopposes the waves of opposite sign. Assume, for example, thatthese devices are batteries, primary or secondary, or continuouscurrent dynamo machines. The waves or impulses of oppositedirection composing the main current have a natural tendency todivide between the two branches; but by reason of the oppositeelectrical character or effect of the two branches, one will offeran easy passage to a current of a certain direction, while the otherwill offer a relatively high resistance to the passage of the samecurrent. The result of this disposition is, that the waves of cur-rent of one sign will, partly or wholly, pass over one of the pathsor branches, while those of the opposite sign pass over the other.There may thus be obtained from an alternating current two ormore direct currents without the employment of any commutator

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