Chapter 131. To define and establish the units of electrical measure
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CHAP. 131.— An Act To define and establish the units of electrical measure.July 12, 1894. *Be it enacted by the Senate and House of Representatives of the United States of America in Congress assembled*,Electrical measure.Units established. That from and after the passage of this Act the legal units of electrical measure in the United States shall be as follows: First. The unit of resistance shall be what is known as the internationalResistance.Ohm. ohm, which is substantially equal to one thousand million units of resistance of the centimeter-gram-second system of electromagnetic 102 units, and is represented by the resistance offered to an unvarying electric current by a column of mercury at the temperature of melting ice fourteen and four thousand live hundred and twenty-one ten-thousandths grams in mass, of a constant cross-sectional area, and of the length of one hundred and six and three-tenths centimeters.
Second. The unit of current shall be what is known as the internationalCurrent.Ampere. ampere, which is one-tenth of the unit of current of the centimeter-gram-second system of electromagnetic units, and is the practical equivalent of the unvarying current, which, when passed through a solution of nitrate of silver in water in accordance with standard specifications, deposits silver at the rate of one thousand one hundred and eighteen millionths of a gram per second. Third. The unit of electromotive force shall be what is known as theMotive force.Volt. international volt, which is the electromotive force that, steadily applied to a conductor whose resistance is one international ohm, will produce a current of an international ampere, and is practically equivalent to one thousand fourteen hundred and thirty-fourths of the electromotive force between the poles or electrodes of the voltaic cell known as Clark’s cell, at a temperature of fifteen degrees centigrade, and prepared in the manner described in the standard specifications.
Fourth. The unit of quantity shall be what is known as the internationalQuantity.Coulomb. coulomb, which is the quantity of electricity transferred by a current of one international ampere in one second. Fifth. The unit of capacity shall be what is known as the internationalCapacity.Farad. farad, which is the capacity of a condenser charged to a potential of one international volt by one international coulomb of electricity. Sixth. The unit of work shall be the Joule, which is equal to tenWork.Joule. million units of work in the centimeter-gram-second system, and which is practically equivalent to the energy expended in one second by an international ampere in an international ohm.
Seventh. The unit of power shall be the Watt, which is equal to tenPower.Watt. million units of power in the .centimeter-gram second system, and which is practically equivalent to the work done at the rate of one Joule per second. Eighth. The unit of induction shall be the Henry, whichInduction.Henry. is the induction in a circuit when the electromotive force induced in this circuit is one international volt while the inducing current varies at the rate of one Ampere per second.
Sec. 2. That it shall be the duty of the National Academy of SciencesDetails to be published. to prescribe and publish, as soon as possible after the passage of this Act, such specifications of details as shall be necessary for the practical application of the definitions of the ampere and volt hereinbefore given, and such specifications shall be the standard specifications herein mentioned. Approved, July 12, 1894.