| 释义 |
Helmholtz Physics.|ˈhɛlmhɒlts|
The name of H. L. F. von Helmholtz (1821–1894), German scientist, used attributively with reference to various devices and theories invented by him. Also Helmˈholtzian a.
1890W. James Princ. Psychol. II. xx. 170 The Helmholtzian theory is probably not the last word in the physiology of hearing. 1920G. B. Shaw How to become Mus. Critic (1960) 311 The Helmholtzian chords of Scriabin. 1930R. Paget Human Speech 8 The ocarina is, I believe, the only well-known wind instrument which operates on the principle of the ‘Helmholtz’ resonator. 1940Chambers's Techn. Dict. 409/2 Helmholtz galvanometer, Helmholtz resonance, Helmholtz resonator. 1962Corson & Lorrain Introd. Electromagn. Fields v. 215 A pair of Helmholtz coils consists of two identical circular current loops placed coaxially so as to obtain uniformity of the magnetic induction B in the region midway between the loops.
▸ Helmholtz free energy n. described by Helmholtz 1882, in Sitzungsber. der Königl. Preuss. Akad. der Wissensch. zu Berlin 33 the thermodynamic function A = U - TS (where U is the internal energy, T the temperature, and S the entropy of the system), representing the amount of energy that can be converted into work at constant temperature. Cf. free energy n. 2.
[1902Encycl. Brit. XXVIII. 167/2 The available energy thus defined differs from E-Tϕ, the free energy of Helmholtz.] 1919Jrnl. Amer. Chem. Soc. 41 986 The negative of the differential of the function of Gibbs, or of the Helmholtz free energy, is defined as [etc.]. 1937M. W. Zemansky Heat & Thermodynamics xi. 195 The Helmholtz function is sometimes called the ‘Helmholtz free energy’, or the ‘free-energy’, but these names are confusing since another function..is also called by some authors the free energy. 1967E. U. Condon & H. Odishaw Handbk. Physics (ed. 2) v. i. 8/1 A system held at constant volume and constant temperature will spontaneously move toward lower values of A. At equilibrium the Helmholtz free energy is a minimum. 2002Proc. National Acad. Sci. U.S.A. 99 14168/1 The difference, at constant volume..and temperature..between the Helmholtz free energy of the virtually incompressible protein–PEG–water system and the pure water system.
▸ Helmholtz function n. (also (rare) Helmholtz's function) (a) described by Helmholtz in Monatsberichte der Königl. Preussischen Akad. der Wissensch. zu Berlin (1868) 224) Math. the transformation of the complex plane Z = 1 / π (ez + z + 1), which arises in the representation of fluid flow through a spout with infinite plane walls (disused); (b) Physical Chem. the equation expressing Helmholtz free energy.
1900Ann. Math. 2 73 If we now allow ε to approach 0 as its limit Z′ approaches *Helmholtz's function, Z1. 1908Ann. Math. 9 77 These functions..effect transformations similar to the Z′'s and Z′′'s obtained from the hyperbolic sine and the Helmholtz function. 1937M. W. Zemansky Heat & Thermodynamics xi. 195 The Helmholtz function is sometimes called the ‘Helmholtz free energy’, or the ‘free-energy’. 1997Proc. Royal Soc. (A.) 4532136 The Helmholtz function, A, (which is related to the internal energy, U, in the same way that the Gibbs function is related to the enthalpy) must be used for the infrared monitored dissociation. |