adiabatic, a. and n. Physics.
(ˌædɪəˈbætɪk, ˌeɪdaɪəˈbætɪk)
[f. Gr. ἀδιάβατ-ος not to be passed through (f. ἀ not + διά through + βατός passable, vbl. adj. f. βα-ίν-ειν to go) + -ic.]
A. adj.
1. Impassable to heat; involving neither loss nor acquisition of heat.
| 1859, 1877 [Implied at sense 2.] 1882 Siemens in Nature XXV. 603 Let us suppose that the attenuated matter in space has a temperature of 160° on the absolute scale, and that it is 3000 times more rarified than when it reaches by adiabatic compression the solar photosphere. 1933 Flight 2 Feb. 99/2 Closed, or adiabatic, cockpits, wherein the pressure could be kept at 430 mm. |
2. adiabatic curve, adiabatic line: a curve or line produced by plotting the changes in volume and pressure of a gas during an adiabatic process; = adiabat.
| 1859 W. J. M. Rankine Man. Steam Engine iii. iii. 302 A certain curve NN passing through A, which may be called a curve of no transmission, or adiabatic curve. Ibid., 346 Each adiabatic line for a perfect gas is a curve of the hyperbolic kind. 1877 Wormell Thermodyn. 130 If a substance can expand without gain or loss of heat, and a curve is drawn, such that the abscissa and ordinate of any point respectively represent the volume of a unit of mass, and the corresponding pressure for unit of area, this curve is termed an adiabatic line. 1922 Glazebrook Dict. Appl. Physics I. 946/2 The calculation fixes a point in the adiabatic line of the pressure-volume diagram for expansion from the initial conditions. 1957 Encycl. Brit. XIV. 178/1 This equation, which gives the form of the adiabatic curves for a perfect gas, shows that these..are steeper than the isothermal curves. 1975 Optics & Spectroscopy XXXIX. 610/1 We calculated the upper bound of the total adiabatic potential curve of the ground state. |
B. n. ellipt. for adiabatic curve; the relationship expressed by an adiabatic curve.
| 1884 Nature 21 Aug. 403/2 Mr. W. Peddie gave a communication on the isothermals and adiabatics of water near the maximum density point. 1928 N. Shaw Man. Meteorol. II. p. xx, The word ‘adiabatic’ is also used as an abbreviation for adiabatic curve which shows the relation between the pressure and temperature of a mass of air when the adiabatic condition is rigorously maintained. 1945 [see adiabat]. 1967 Condon & Odishaw Handbk. Physics (ed. 2) iii. ii. 24/1 This Hugoniot adiabatic is shown in Fig. 2.5 in comparison with the usual isentropic adiabatic. |
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Add: Hence adiabaˈticity n., the condition of being adiabatic; the degree to which something is adiabatic.
| 1965 Jrnl. Chem. Physics XLIII. 1605/2 In the activated-complex expression..vibrational adiabaticity was assumed only in the immediate vicinity of the activated complex. 1983 M. S. Rabinovich in Galeev & Sudan Basic Plasma Physics I. i. 7 The adiabaticity parameter. 1989 Nature 29 June 691/1 Giving a correction to adiabaticity of the order of (k/µ)/(1/r)≃(r/µ)1/2{ltlt}1 . |