Electricity for public schools and colleges . regard thecell as a contrivance in which electricity is pumped up from alower level to a higher by the expenditure of chemical energy ;the electricity running down through the external circuit to thelower level again, and so on continuously. In the simple diagram here given the cell is represented bythe vertical line C Z. This indicates that in the cell the elec-tricity is raised from a lower to a higher level by expenditure ofchemical energy ; and that thenf^=^. the electricity flows down fromthe higher level C to the lowerlevel Z through the exte
Electricity for public schools and colleges . regard thecell as a contrivance in which electricity is pumped up from alower level to a higher by the expenditure of chemical energy ;the electricity running down through the external circuit to thelower level again, and so on continuously. In the simple diagram here given the cell is represented bythe vertical line C Z. This indicates that in the cell the elec-tricity is raised from a lower to a higher level by expenditure ofchemical energy ; and that thenf^=^. the electricity flows down fromthe higher level C to the lowerlevel Z through the externalcircuit X. We may here add that it isusual to call the zinc the , and the copper the — plate; while the copper wire soldered tothe zinc plate is the — pole, and that soldered to the copper plateis the + pole. In fact, that plate or pole is called -I- fromwhich the current flows to the other plate or pole current flows from zinc to copper through the liquid, andfrom copper to zinc through the external cii. XI. THE PHENOMENA OF ELECTRIC CURRENTS 173 The phenomena of the open cell are, we see, electrostatic ;the A V of the terminals may be observed with a quadrant elec-trometer. When the circuit is completed we get a flow of elec-tricity ; the phenomena accompanying this flow will be surveyedin Chapter XII. § 8. Digression on the Galvanometer.—In Chapter student will find discussed the construction and theory of thegalvanometer. We shall, therefore, deal with it very briefly here. The figures of Chapter XVII. indicate that when a currentpasses along a wire held parallel to a magnetic needle, above orbelow it, the current produces a magnetic field that tends to setthe needle in a position at right angles to the wire. As the needleis deflected, the earths couple, tending to restore it to itsoriginal position of rest in the plane of the magnetic meridian,becomes greater ; while the disturbing couple due to the currentbecomes less
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