等效 等價 當量
1. Equal in worth or value, force, power, effect, import, and the like; alike in significance and value; of the same import or meaning.
For now to serve and to minister, servile and ministerial, are terms equivalent. --South.
2. Geom. Equal in measure but not admitting of superposition; -- applied to magnitudes; as, a square may be equivalent to a triangle.
3. Geol. Contemporaneous in origin; as, the equivalent strata of different countries.
1. Something equivalent; that which is equal in value, worth, weight, or force; as, to offer an equivalent for damage done.
He owned that, if the Test Act were repealed, the Protestants were entitled to some equivalent.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.
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.
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.
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.
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 10⁷ 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.
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° C. to 1° C., or from 32° F. to 33° 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.
E·quiv·a·lent, v. t. To make the equivalent to; to equal; equivalence. [R.]
adj 1: equal in amount or value; "like amounts"; "equivalent
amounts"; "the same amount"; "gave one six blows and
the other a like number"; "an equal number"; "the same
number" [syn: like, equal, same] [ant: unlike]
2: being essentially equal to something; "it was as good as
gold"; "a wish that was equivalent to a command"; "his
statement was tantamount to an admission of guilt" [syn: tantamount(p)]
n 1: a person or thing equal to another in value or measure or
force or effect or significance etc; "send two dollars
or the equivalent in stamps"
2: the atomic weight of an element that has the same combining
capacity as a given weight of another element; the
standard is 8 for oxygen [syn: equivalent weight, combining