Joule's equivalent
Equivalent E*quiv"a*lent ([-e]*kw[i^]v"[.a]*lent), n. 1. Something equivalent; that which is equal in value, worth, weight, or force; as, to offer an equivalent for damage done. [1913 Webster]

He owned that, if the Test Act were repealed, the Protestants were entitled to some equivalent. . . . During some weeks the word equivalent, then lately imported from France, was in the mouths of all the coffeehouse orators. --Macaulay. [1913 Webster]

2. (Chem.) That comparative quantity by weight of an element which possesses the same chemical value as other elements, as determined by actual experiment and reference to the same standard. Specifically: (a) The comparative proportions by which one element replaces another in any particular compound; thus, as zinc replaces hydrogen in hydrochloric acid, their equivalents are 32.5 and 1. (b) The combining proportion by weight of a substance, or the number expressing this proportion, in any particular compound; as, the equivalents of hydrogen and oxygen in water are respectively 1 and 8, and in hydric dioxide 1 and 16. [1913 Webster]

Note: This term was adopted by Wollaston to avoid using the conjectural expression atomic weight, with which, however, for a time it was practically synonymous. The attempt to limit the term to the meaning of a universally comparative combining weight failed, because of the possibility of several compounds of the substances by reason of the variation in combining power which most elements exhibit. The equivalent was really identical with, or a multiple of submultiple of, the atomic weight. [1913 Webster]

3. (Chem.) A combining unit, whether an atom, a radical, or a molecule; as, in acid salt two or more equivalents of acid unite with one or more equivalents of base. [1913 Webster]

{Mechanical equivalent of heat} (Physics), originally defined as the number of units of work which the unit of heat can perform, equivalent to the mechanical energy which must be expended to raise the temperature of a pound of water one degree Fahrenheit; later this value was defined as one {British thermal unit} (B.t.u). Its value was found by Joule to be 772 foot pounds; later measurements give the value as 777.65 foot-pounds, equivalent to 107.5 kg-meters. This value was originally called Joule's equivalent, but the modern Joule is defined differently, being 10^{7} ergs. The B.t.u. is now given as 1,054.35 absolute Joules, and therefore 1 calorie (the amount of heat needed to raise one gram of water one degree centigrade) is equivalent to 4.186 Joules. [1913 Webster + PJC]

Note: The original definition of the Mechanical equivalent of heat in the 1913 Webster was as below. The difference between foot pounds and kilogram-meters ("on the centigrade scale") is puzzling as it should be a factor of 7.23, and the figure given for kilogram-meters may be a mistaken misinterpretation of the report. -- PJC: The number of units of work which the unit of heat can perform; the mechanical energy which must be expended to raise the temperature of a unit weight of water from 0[deg] C. to 1[deg] C., or from 32[deg] F. to 33[deg] F. The term was introduced by Dr. Mayer of Heilbronn. Its value was found by Joule to be 1390 foot pounds upon the Centigrade, or 772 foot pounds upon the Fahrenheit, thermometric scale, whence it is often called {Joule's equivalent}, and represented by the symbol J. This is equal to 424 kilogram meters (Centigrade scale). A more recent determination by Professor Rowland gives the value 426.9 kilogram meters, for the latitude of Baltimore. [1913 Webster +PJC]


The Collaborative International Dictionary of English. 2000.

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  • Joule's equivalent — joule joule (j[=oo]l), n. [From the distinguished English physicist, James Prescott Joule (1818 1889).] (Physics.) A unit of work which is equal to 10^{7} ergs (the unit of work in the C. G. S. system of units), and is equivalent to one watt… …   The Collaborative International Dictionary of English

  • Joule's equivalent — n MECHANICAL EQUIVALENT OF HEAT …   Medical dictionary

  • Joule’s equivalent — mechaninis šilumos ekvivalentas statusas T sritis fizika atitikmenys: angl. Joule’s equivalent; mechanical equivalent of heat vok. mechanisches Wärmeäquivalent, n rus. механический эквивалент теплоты, m pranc. équivalent mécanique de la calorie,… …   Fizikos terminų žodynas

  • joule's equivalent — noun Usage: usually capitalized J Etymology: after J. P. Joule : mechanical equivalent of heat …   Useful english dictionary

  • Joule's equivalent — see mechanical equivalent of heat …   Useful english dictionary

  • Joule's laws — are a pair of laws concerning the heat produced by a current and the energy dependence of an ideal gas to that of pressure, volume, and temperature, respectively. Joule s first law, also known as the Joule effect, is a physical law expressing the …   Wikipedia

  • Joule's law — Physics. 1. the principle that the rate of production of heat by a constant direct current is directly proportional to the resistance of the circuit and to the square of the current. 2. the principle that the internal energy of a given mass of an …   Universalium

  • Equivalent — E*quiv a*lent ([ e]*kw[i^]v [.a]*lent), n. 1. Something equivalent; that which is equal in value, worth, weight, or force; as, to offer an equivalent for damage done. [1913 Webster] He owned that, if the Test Act were repealed, the Protestants… …   The Collaborative International Dictionary of English

  • joule — (j[=oo]l), n. [From the distinguished English physicist, James Prescott Joule (1818 1889).] (Physics.) A unit of work which is equal to 10^{7} ergs (the unit of work in the C. G. S. system of units), and is equivalent to one watt second, the… …   The Collaborative International Dictionary of English

  • Joule — Einheit Norm SI Einheitensystem Einheitenname Joule Einheitenzeichen J Beschriebene Größe(n) Arbeit; Energie; innere Energie; Wärme (Wärmemenge) …   Deutsch Wikipedia

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