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 363
pondiametrically opposite points of the two-part commutator. (a) Upon revolving the shaft slowly the needle is now deflectedto one side of the zero mark. (b) Reverse the directionof rotation, and the directionof deflection (or polarity ofthe brushes) is now reversed. (c) Increase the speedand the… … Direction of current in the coil at one-half revolution from the position in Fig. 316. Brush M is positive as before.
Electricity · Magnetism
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