(watts)

(a) The practical unit of electric activity, rate of work, or rate of energy. It is the rate of energy or of work represented by a current of one ampere urged by one volt electro-motive force; the volt-ampere. It is the analogue in electricity of the horse power in mechanics; approximately, 746 watts represent one electric horse power. Ohm's law, taken as C = E/R, gives as values for current, C and E/R, and for electro- motive force C R. In these formulas, C represents current strength, R represents resistance and E represents electro-motive force. Then a watt being the product of electro-motive force by current strength, we get the following values for rate of electric energy, of which the watt is the practical unit: (1) E2/R -- (2) C*E -- (3) C2 * R. The equivalents of the watt vary a little according to different authorities. Ayrton gives the following equivalents: 44.25 foot pounds per minute--.7375 foot pounds per second--1/746 horse power. These values are practically accurate. Hospitalier gives .7377 foot pounds per second. Hering gives .737324 foot pounds per second, and 1000/745941 horse power. It is equal to 1E7 ergs per second. Synonym--Volt-ampere. (c) It has been proposed to use the term as the unit of energy, instead of activity or rate of energy (Sir C. W. Siemens, British Association, 1882); this use has not been adopted and may be regarded as abandoned. [Transcriber's note; Watt is a unit of POWER--energy per unit of time.]