Gage, Alfred P. (Alfred Payson), 1836-1903 · Boston, London, Ginn · leaf 588
a per-manent steel magnet cannot be made as powerful as anelectro-magnet having a soft iron core of equal mass. Fig. 461 illustrates a separately excited dynamo, where thefield magnet ooils receive their currents from a separategenerator, e.g. a battery, and not from the armature coils. 1 For the…
Physics
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