Elementary lessons in electricity and magnetism (1906)
Thompson, Silvanus P. (Silvanus Phillips), 1851-1916, Schwetzky, Otto H. L. [from old catalog] · Chicago, Thompson & Thomas · leaf 86
adopted, A thin strip orneedle of metal is suspended so asto turn about a point C It is elec-trified from a known source. Underit are placed (Fig. 39) two semicir-cular discs, or half-rings of dissimilarmetals. Neither attracts or repels^. the electrified needle until the two are brought into… … CHAP. I.] ELECTRICITY AND MAGNETISM. 69 72. Volta found, moreover, that the differences ofelectric potential between the different pairs of metalswere not all equal. Thus, while zinc and lead wererespectively + and - to a slight degree, he found zincand silver to be respectively + and - to a much…
Electricity · Magnetism
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