Lessons in practical electricity; principles, experiments, and arithmetical problems, an elementary text-book (1902)
Swoope, Coates Walton. [from old catalog] · New York, D. Van Nostrand company · leaf 65
long, test it for polarity, and then hold it in one hand in tliemagnetic meridian, with one end pointing or dipping down-ward at an angle of about 70 degrees to the horizontal. Fig.64. Strike the bar several hard blows with a hammer, andthen test for polarity. The lower end will be found to… … magnetised and i)ec()ines N-seeking. The eartlis field hasinduced poles in the bar by induction, the hammer blowsimply assisting the molecules to turn around according to the molecular theory. In alike manner tests made witha compass needle on iron andsteel girders in buildingsunder construction,…
Electricity · Magnetism
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