Electricity for public schools and colleges . each coil acts in one direction through this 180° ofrotation ; and the coils are so wound that the of B andB act in one direction. Through the second 180° of rotation are reversed ; but a commutator, described in § 4, main-tains the current in a constant direction in the external circuit. The direction of current can easily be predicted from Lenzslaw ; for, as B leaves the N pole of the magnet and approaches c c 386 ELECTRICITY en. XXIII. the S pole, it will acquire on the side turned towards the magneta S polarity, or the curren
Electricity for public schools and colleges . each coil acts in one direction through this 180° ofrotation ; and the coils are so wound that the of B andB act in one direction. Through the second 180° of rotation are reversed ; but a commutator, described in § 4, main-tains the current in a constant direction in the external circuit. The direction of current can easily be predicted from Lenzslaw ; for, as B leaves the N pole of the magnet and approaches c c 386 ELECTRICITY en. XXIII. the S pole, it will acquire on the side turned towards the magneta S polarity, or the current will there run clock-wise, since thiswill oppose the motion. By giving a rapid motion and having many turns of wire weincrease the a and the )ii of § 2, or increase the induced can thus get an large enough to give shocks andsmall sparks. § 4. The Simple Commutator.—The figure here given repre-sents a simple form of commutator. The one end of the wire issoldered to the metal piece 0, and the other to 0 ; these pieces. pass each nearly half-way round the axis J, but are insulated fromone another by two slits, one of which is seen in the axis itself is of ivory, ebonite, or some other insulatingmaterial. The circuit is completed by means of the metal springsb and c. Just as the coils are passing the position in which change direction, the metal springs b and c cross the twoslits and come into contact each with that metal piece {0 or 0)that was just before in contact with the other spring. Thus theexternal current is maintained constant in direction. The other metal piece, shown in the ligure, is for anotherpurpose that we need not describe. CH. xxiir. DYNAMO-ELECTRIC MACHINES 387 § 5. Siemenss Armature.—^^e may here mention that thesystem of core and coil, in which the is induced, is calledan armature. In order to get the coil into a powerful field closeto the magnets, Siemensinventeda very compact form of armature.
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Keywords: ., bookcentury1800, bookdecade1890, bookpubl, booksubjectelectricity
