| 释义 |
joule Physics.|dʒuːl|
Also Joule.
[Named 1882, after Dr. J. P. Joule, an English physicist.]
1. An electrical unit, being the amount of work done (or of heat generated) by a current of one ampère acting for one second against a resistance of one ohm. Later adopted as the M.K.S. unit of energy and work in non-electrical contexts also; it is equal to 10 million ergs, and is now incorporated in the International System of Units, in which it is given the equivalent definition of the work done when the point of application of a force of one newton is displaced through a distance of one metre in the direction of the force.
Although some people of this name call themselves |dʒaʊl| and others |dʒəʊl| (D. Jones Everyman's Eng. Pronouncing Dict. (ed. 11, 1956), G. M. Miller BBC Pronouncing Dict. British Names (1971)), it is almost certain that J. P. Joule (and some at least of his relatives) used |dʒuːl|. For evidence on this point see Nature (1943) CLII. 354, 418, 479, 602.
1882Athenæum 26 Aug. 274/2 Dr. Siemens proposes to add to these [electrical] units four new ones, as follows: (1) a Watt..(2) a Weber..(3) a Gauss..(4) a unit of heat, to be called a ‘Joule’, and to be defined as the quantity of heat generated by an ampère flowing through an ohm for one second. Ibid. 2 Sept. 310/2 Two of his units were unanimously approved—namely, (1) the watt..(2) the joule. 1886J. A. Fleming Short Lect. to Electr. Artisans v. 87 An amount of work equal to 10 million ergs is called one joule. Hence one foot-pound = 1·356 joules, or one joule = ·7373 foot-pound. 1889Rep. Brit. Assoc. Adv. Sci. 1888 56 It was also agreed to adopt the name ‘Joule’ for 107 C.G.S. units of work. Thus a Joule is equal to 107 ergs. It is the work done in one second by a power of one Watt. 1893Operator & Electr. World 2 Sept. 175/1 The several governments represented by the delegates of this International Congress of Electricians..hereby recommended to formally adopt as legal units of electrical measure the following... As a unit of work the joule, which is 107 units of work in a C.G.S. system. 1896Rep. Brit. Assoc. Adv. Sci. 1896 154 The amount of heat required to raise the temperature of 1 gramme of water 1° C. of the scale of the hydrogen thermometer, at a mean temperature which may be taken as 10° C. of that thermometer, is 4·2 Joules. 1923N. Shaw Forecasting Weather (ed. 2) i. 24 Observations for nine stations within greater London, comprising measures of atmospheric pollution at Richmond and South Kensington, total solar radiation at South Kensington in joules, and its average and maximum rate in milliwatts. 1949Nature 19 Mar. 428/1 It was also agreed [by the ninth International Conference of Weights and Measures] that the unit of heat should be the ‘Joule’. 1951Engineering 11 May 577/1 The international units, as realised in the various national laboratories, differed by small amounts, but it has been agreed that the mean international joule of the various laboratories is equal to 1·00019 absolute joules. Ibid. 577/3 If the value of the 15-deg. calorie is taken as 4·1855 absolute joules, a B.Th.U. is equal to 1054·54 absolute joules. 1963[see calorie]. 1970Daily Tel. 4 May 3 Adoption of the metric system and loss of the calorie as a unit of energy may increase the hazard of obesity, Prof. J. B. M. Coppock, an expert on nutrition, said yesterday... There was a danger of losing the calorie for another unit, the joule, which was little understood outside physics and engineering... It would be years before the public..could adjust to a new jargon.
2. Used attrib. and in the possessive as the personal name to designate quantities, effects, etc., discovered by Joule or arising out of his work: Joule († or Joule's) effect, (a) the heating effect of an electric current flowing through a resistance (described by Joule's law (a)); (b) a change in the linear dimensions (esp. length) of a body when it is subjected to a magnetic field; Joule's equivalent= mechanical equivalent of heat: see equivalent n. 3 c.; Joule heating, the heating that occurs when an electric current flows through a resistance; Joule's law, (a) the law that the heat produced by an electric current i flowing through a resistance R for a time t is proportional to i2Rt; (b) a law concerning ideal gases, now usually given in the form: the internal energy of a given mass of a gas depends only on its temperature; ˈJouleˌmeter, a meter in which the Joule is used as the unit of work or energy.
¶ See also Joule-Kelvin, Joule-Thomson.
1879Encycl. Brit. VIII. 57/2 In general the Peltier effect is..mixed up with Joule's effect, and makes itself felt by producing a disturbance at the junction. 1914Physical Rev. IV. 499 If the change in length of AC is measured as the field, H, is varied, we have the ordinary longitudinal Joule effect, whereas if DB or the length normal to the page is measured we have the transverse Joule effect. 1931S. R. Williams Magn. Phenomena ii. 108 In the Joule effect the changes in length are..very small. Ibid. 111 (heading) Transverse Joule effect—change in dimensions normal to the magnetic field. 1933J. E. Phillips Intermediate Magn. & Electr. xiii. 303 The Peltier effect..is proportional to the first power of the current, while the Joule effect varies as the square of the current. 1939L. F. Bates Mod. Magn. x. 303 The existence of a Joule effect in non-ferromagnetic substances was first proved by Kapitza. 1966F. Brailsford Physical Princ. Magn. vi. 143 Additional to the high-field volume change is the Joule effect involving changes in linear dimensions in relatively low fields, which in most cases may be 10 to 100 times greater than those due to the volume magnetostriction.
1853W. J. M. Rankine in Trans. R. Soc. Edin. XX. 192 This last quantity..is..one-ninth of the value according to Mr Joule's equivalent. 1853W. Thomson in Ibid. 298 In terms of Joule's mechanical equivalent of heat. 1912H. A. Perkins Introd. Gen. Thermodynamics ii. 19 The numerical constant connecting heat energy..and mechanical energy..is known as ‘Joule's equivalent’. 1958A. J. Woodall Heat v. 99 Joule's equivalent is, of course, expressible in different units.
1929J. A. Ratcliffe Physical Princ. Wireless iv. 57 The known forms of A.C. galvanometer, which depend on Joule heating. 1971Physics Bull. Apr. 207/3 Some of the power generated is wasted by joule heating within the element.
1855W. Thomson in Proc. Philos. Soc. Glasgow III. 286 We thus have an equation between the diminution of the electrical energy in any infinitely small time, and the expression according to Joule's law for the heat generated in the same time in the discharges multiplied by the mechanical equivalent of the thermal unit. 1879Encycl. Brit. VIII. 57/1 The current of the battery heats the pile in part uniformly according to Joule's law. 1887Ibid. XXII. 480/1 Joules law... When a gas expands without doing external work, and without taking in or giving out heat, its temperature does not change... We must therefore conclude that the internal energy of a given mass of a gas depends only on its temperature, and not upon its temperature or volume. 1945R. H. Frazier Elem. Electr.-Circuit Theory i. 21 Ohm's law and Joule's law are interdependent; either can be derived from the other. 1951C. L. Brown Basic Thermodynamics vi. 83 For a perfect gas the internal energy is a function of temperature only. This statement, known as Joule's law after its formulator, can be expressed symbolically as u = f(T). |