| 释义 |
Kelvin, kelvin|ˈkɛlvɪn|
[The title of Sir William Thomson, Lord Kelvin (1824–1907), British physicist and inventor.]
†1. (With lower-case initial.) A name proposed (but little used) for the kilowatt-hour, the ordinary commercial unit of electric energy. Obs.
1892Electrician 6 May 1/1 The President of the Board of Trade having cordially approved and Lord Kelvin having acquiesced; after the word ‘unit’ in the Provisional Orders of this year, the words ‘hereinafter called a kelvin’ will be introduced. 1911Encycl. Brit. XXVII. 740/1 The corresponding energy unit being the kilowatt-second, and 3600 kilowatt-seconds or 1 kilowatt-hour called a ‘Board of Trade unit’ or a ‘kelvin’.
2. (With capital initial.) Used attrib. and in the possessive to designate instruments and concepts devised by Lord Kelvin, as Kelvin balance, an electrical measuring instrument having a set of horizontal coils arranged in the form of a balance with a sliding weight, which is used to balance the electromagnetic forces produced by a current passed through the coils and so to measure its strength; Kelvin (double) bridge, a modification of the Wheatstone bridge used for measuring low resistances and having two pairs of variable ratio resistors, an adjustable standard resistor, and the unknown one; Kelvin's law, the law that the most economical cross-sectional area of a conductor used as a transmission line is that for which the cost of the energy dissipated in any period is equal to the charges during the same period on the capital cost of the line.
1896Proc. Physical Soc. XIV. 166 A convenient method for determining low resistances, such as..a Kelvin bridge. 1903F. A. C. Perrine Conductors for Electr. Distribution viii. 160 (heading) Kelvin's law of economy in conductors. 1904Swenson & Frankenfield Testing Electro-Magn. Machinery I. 122 The Kelvin Balance is recognized as a standard instrument. 1906Rep. Brit. Assoc. Adv. Sci. 119 The current leads of standard resistances intended for measurement on the Kelvin double bridge should have a resistance not greater than the standard itself. 1933E. W. Golding Electr. Measurements ii. 14 Kelvin balances are manufactured with ten different ranges up to 2,500 amp. 1957W. J. John Mod. Electr. Engin. III. x. 301/2 Kelvin's law is usually expressed in terms of annual costs, though it is equally true of capitalized costs. 1967H. Cotton Adv. Electr. Technol. iii. 92 Calculate the current flowing in the galvanometer of the Kelvin double-bridge circuit.
3. (With capital initial.) Used attrib. to designate an absolute scale of temperature (defined thermodynamically in terms of the operation of an ideal heat engine) in which the zero is identified with absolute zero and values are assigned to one or more fixed points so as to make the degrees correspond in size to those of the centigrade (Celsius) scale. So Kelvin temperature, a temperature expressed in terms of this scale.
As the scale was orig, defined, the temperature interval between two fixed points (the freezing point and the boiling point of water) was made to be exactly 100 degrees, so that the value of each point was a matter of experiment (which produced values of about 273° and 373° respectively); in 1954 the scale was redefined in terms of a single fixed point, the triple point of water, to which was assigned the value 273·16° exactly (giving a figure of approximately 273·15° for the ice point).
[1871J. C. Maxwell Theory of Heat viii. 155 (heading) Thomson's absolute scale of temperature. 1899W. Watson Text-bk. Physics vi. 334 The temperatures..are 283°, 293°,..on Lord Kelvin's absolute scale.] 1908Amer. Jrnl. Sci. CLXXVI. 421 The derivation of the Kelvin thermodynamic scale from the expansion of nitrogen. 1922Glazebrook Dict. Appl. Physics I. 270/2 If the same size of degree be adopted for the Kelvin scale, then..the readings, on either scale, will be identical. 1937M. W. Zemansky Heat & Thermodynamics ix. 140 Two temperatures on the Kelvin scale are to each other as the heats absorbed and rejected respectively by a Carnot engine operating between reservoirs at these temperatures. Ibid. 144 The Kelvin temperature is therefore numerically equal to the absolute temperature and may be measured with a gas thermometer. 1958Condon & Odishaw Handbk. Physics v. iii. 30/2 This new absolute thermodynamic scale, called the Kelvin scale, does not differ from the thermodynamic ‘centigrade’ scale by an amount which can be determined experimentally at the present time. 1962Units & Standards of Measurement: Temperature (Nat. Physical Lab.) 3 The thermodynamic Kelvin scale..is recognized as the fundamental scale to which all temperature measurements should ultimately be referred.
b. degree Kelvin (or Kelvin degree): a degree of the Kelvin scale (in size equal to the degree centigrade), symbol °K (see K 4 f); now formally called a kelvin (symbol K) and incorporataed into the International System of Units as a basic unit.
1911Physical Rev. XXXIII. 220 The writer has assumed that the degree Kelvin and the degree centigrade were equal. 1930Engineering 9 May 595/3 A perfect gas of one free electron per atom would necessarily contribute three calories per gram-atom per degree Kelvin to the specific heat of the metal. 1941Temperature (Amer. Inst. Physics) 11 When using the Thermodynamic Centigrade Scale one is simply expressing the number of Kelvin degrees that a particular thermal state is above or below the ice point. 1945G. R. Noakes Text-bk. Heat i. 26 The name ‘degrees Kelvin’ (°K.) is used for the true absolute scale temperature, and ‘degrees absolute’ (°A., or °abs.) for temperatures measured by other means on any other scale numbered up from absolute zero. 1962Corson & Lorrain Introd. Electromagn. Fields iii. 108, T is the absolute temperature in degrees Kelvin. 1968Nature 16 Nov. 651/2 Resolution No. 3 [of the thirteenth General Conference of Weights and Measures] changes the name of the ‘degree Kelvin’ (symbol °K) simply to ‘kelvin’, with symbol K... The terms of the revised definition of the unit of thermodynamic temperature are (resolution No. 4): ‘the kelvin..is the fraction 1/273·16 of the thermodynamic temperature of the triple point of water’. 1971Physics Bull. Mar. 144/1 The inversion transitions..indicate that the ammonia molecules are at a temperature of several tens of kelvin. 1973Sci. Amer. Aug. 84/3 Only liquid hydrogen will serve, and it must be stored at an extremely low temperature (22 degrees Kelvin, or 22 degrees Celsius above absolute zero). |