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 58
netic body placed between or near, but not touching,the poles of a magnet, and is free to be rotated or moved toand from the poles. A different type of armature from thatused in a dynamo is illustrated in Figs. 52 and 53, where apiece of iron is attracted to the poles againstthe action of a spring.… … Fig. 53.—PolarizedArmature. Fig. 54.—HorseshoeMagnet with Keeper. The magnetism induced in the keeper reacts on the magnet,and not only helps to maintain the strength of the magnet,but also serves to augment it. A magnet deprived of itskeeper gradually loses its magnetism. Steel is much morereadily…
Electricity · Magnetism
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