Electricity for public schools and colleges . Fig. i. In this experiment it is assumed as sufficiently proved by various con-vergent pieces of evidence that the zinc, held in the moistened hand, ispractically at the zero-V of the earth ; and that the contact of the copper withthe brass of the electroscope gives no A V. Hence, it is argued, the electroscope or electrometer indicates the A V dueto the contact of the zinc and copper alone, and shows that zinc is -I- tocopper. (ii.) An electroscope is provided with an upper condensing plate made ofzinc. This is, as usual, provided on its under sur
Electricity for public schools and colleges . Fig. i. In this experiment it is assumed as sufficiently proved by various con-vergent pieces of evidence that the zinc, held in the moistened hand, ispractically at the zero-V of the earth ; and that the contact of the copper withthe brass of the electroscope gives no A V. Hence, it is argued, the electroscope or electrometer indicates the A V dueto the contact of the zinc and copper alone, and shows that zinc is -I- tocopper. (ii.) An electroscope is provided with an upper condensing plate made ofzinc. This is, as usual, provided on its under surface with an insulating layerof lac varnish. Both plates are as usual carefully discharged by means of aBunsens flame, until no movement of the leaves is observed on raising orlowering the upper plate. CH, XI. THE PHENOMENA OF ELECTRIC CURRENTS 16/. Then a copper wire is made to connect the upper (unvarnished) surface ofthe zinc plate with the under surface of the copper plate. It is found that the zinc and copper have now assumed a A V in which thezinc is + to the copper. This AV is of course (j^f Chapter X.) magnified,and so rendered evident, when the wire isremoved and the upper condensing plate islifted away. Here there is no doubtful con-tact of metal and wet hand. (iii.) If in experiment (i.) we hold thecopper end of the compound bar, and touchthe plate of the gold-leaf electroscope withthe zinc, we get no result. This supportsVoltas conclusion (3). So if we make a bar of zhic j gold \ iron \coppe?-, and use it as in (i.), we get the sameresult as in (i.). (iv.) If we hold the copper end of the barand insert a piece of wet paper between thezinc and the gold-leaf electroscope, we shallfind that, on removing the bar and raisingthe upper condensing plate, the lower plate Fig. ii. is at a -^- V. Voltas view would be that the co
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Keywords: ., bookcentury1800, bookdecade1890, bookpubl, booksubjectelectricity
