Lessons in practical electricity; principles, experiments, and arithmetical problems, an elementary text-book (1903)
Swoope, Coates Walton. [from old catalog] · New York, D. Van Nostrand company · leaf 357
e direction ofcurrent in the wires AB, and CD, is reversed, Flemings rule,and current flows from D to C, through brush P, now positive,then through the lamps in the opposite direction to that inFig. 307, and through brush M, now negative, to AB, to D,etc. In every revolution the polarity of the… … At the instant depicted in the revolutionbrush M is positive. DYNAMO ELECTRIC MACHINES. 339 tiplied by the number of poles. The number of times whichthe alternations occur is usually expressed simply as the fre-quency, thus, a frequency of 7200 alternations per minutemeans 7200 reversals of…
Electricity · Magnetism
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