| 释义 |
▪ I. Maxwell1|ˈmækswɛl|
The name of Charles Maxwell, 19th-century English soldier and explorer, used in the possessive to designate Maxwell's duiker, a small brown West African antelope, Cephalophus maxwelli, brought back from Sierra Leone by him.
[1827E. Griffith et al. tr. Cuvier's Animal Kingdom IV. 267 Maxwell's Antelope. (A. Maxwellii.) A specimen somewhat inferior in size was brought home from Sierra Leone by Colonel Charles Maxwell.] 1905Sclater & Thomas Bk. Antelopes I. 182 Maxwell's Duiker appears to extend from Senegal and Gambia all along the west coast of Africa to the mouths of the Niger. 1960Times 29 Sept. (Nigeria Suppl.) p. xxi/4 The little Maxwell's duiker..is everywhere abundant.
▪ II. Maxwell2 Physics.|ˈmækswɛl|
[The name of James Clerk Maxwell (1831-79), Scottish physicist.]
1. Used in the possessive and attrib. to designate various concepts originated by him, as Maxwell('s) demon, a being imagined by Maxwell as allowing only fast-moving molecules to pass through a hole in one direction and only slow-moving ones in the other direction, so that if the hole is in a partition dividing a gas-filled vessel into two parts one side becomes warmer and the other cooler, in contradiction to the second law of thermodynamics; Maxwell('s) distribution, the distribution of molecular velocities predicted by Maxwell's law, the number with a velocity between v and v+dv being proportional to exp(-½mv2/kT)v2dv (where m is the mass of a molecule, k is Boltzmann's constant, and T is the absolute temperature); Maxwell('s) equation, each of a set of four linear partial differential equations (first proposed by Maxwell in 1864) which summarize the classical properties of the electromagnetic field and relate space and time derivatives of the electric and magnetic field vectors, the electric displacement vector, and the magnetic induction vector, and also involve the electric current and charge densities; usu. pl.; Maxwell('s) law, a law in classical physics giving the probabilities of different velocities for the molecules of a gas in equilibrium.
1879W. Thomson Pop. Lect. & Addresses (1889) I. 137 Clerk *Maxwell's ‘demon’ is a creature of imagination.., invented to help us to understand the ‘Dissipation of Energy’ in nature. 1885Science 31 July 83/1 (heading) Maxwell's demons. 1956E. H. Hutten Lang. Mod. Physics iv. 152 It would require a Maxwell demon..to select the rapidly moving molecules according to their velocity and concentrate them in one corner of the vessel. 1971Sci. Amer. Sept. 182/2 Maxwell's demon became an intellectual thorn in the side of thermodynamicists for almost a century. The challenge to the second law of thermodynamics was this: Is the principle of the increase of entropy in all spontaneous processes invalid where intelligence intervenes?
1899R. E. Baynes tr. Meyer's Kinetic Theory of Gases 370 If the number of particles is limited..*Maxwell's distribution cannot exist at every moment, but will occur with exactness only when the changing states which succeed each other in the course of a sufficiently long period are all taken into account together. 1955Friedman & Weisskopf in W. Pauli Niels Bohr 138 The spectrum of neutrons and protons emitted from nuclei bombarded with neutrons of 14 Mev or with protons of similar energy fits approximately the predicted Maxwell distribution of an evaporating compound nucleus.
1907Sci. Abstr. A. X. 1295 The principle of relativity in conjunction with *Maxwell's equation leads to the conclusion that the inertia of a body changes in a quite determinate manner with its energy-content. 1962Corson & Lorrain Introd. Electromagn. Fields iii. 101 If the symmetry of the [electrostatic] field is simple and if the charge density ρ is zero, as it often is, we can usually integrate the Maxwell equation ∇·D = ρ to find the displacement vector D. 1964E. A. Power Introd. Quantum Electrodynamics i. 4 Maxwell's equations are not invariant under Galilean invariance and thus are not valid in all inertial frames. Historically this was a most important result leading to special relativity.
1899R. E. Baynes tr. Meyer's Kinetic Theory of Gases iii. 48 That this extension of *Maxwell's law to compound molecules is admissible was first recognised by Boltzmann. 1943Margenau & Murphy Math. Physics & Chem. xii. 432 The Maxwell law for the distribution of velocities in an ideal gas.
2. (Usu. written maxwell.) The unit of magnetic flux in the C.G.S. system, equal to the flux through an area of one square centimetre normal to a uniform induction of one gauss.
In the International System of Units the unit of magnetic flux is the weber (= 108 maxwells).
1900Nature 30 Aug. 414/1 The Commission proposes to assign to the unit of magnetic flux, of which the magnitude will be subsequently defined, the name of Maxwell. 1924A. Still Elem. Electr. Design iv. 68 It is desired to estimate the total flux in maxwells carried by a closed circular iron ring. 1959R. L. Shrader Electronic Communication iii. 72 The gauss is the flux density in maxwells per square centimeter. |