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تسجيل

Unit of Electromotive Force, the Volt

المؤلف:  GEORGE A. HOADLEY

المصدر:  ESSENTIALS OF PHYSICS

الجزء والصفحة:  p-356

2025-12-29

693

The volt is the difference of potential required at the ends of a conductor, the resistance of which is 1 ohm, to send through it a current of 1 ampere.

The E. M. F. of a cell depends only upon the materials of which it is composed, and not at all upon its size or shape. The gravity cell gives nearly 1.1 volts; the Leclanché cell, about 1.5 volts; and the chromic acid cell, about 2 volts. Many attempts have been made to produce a standard cell. In such a cell it is not at all essential that the E. M. F.

should be 1, but the E. M. F., whatever it is, should remain constant. The legal standard cell in the United States is the Clark cell. Its E. M. F. is 1.434 volts at 15° C. The Weston or cadmium standard cell has an E. M. F. of 1.0186 volts between 5° C. and 26° C. The standard cell is not used for the production of a current but for comparing its voltage with that of other cells.