| 释义 |
potential, a. and n.|pəʊˈtɛnʃəl|
Also 4–6 -encial(l.
[ME. potenciall, ad. late L. potentiālis (Albertus Magnus a 1250, but cf. potentiāliter adv. 5th c., Sidon.), f. potentia potency + -al1; so OF. potencial (14–15th c. in Godef.), mod.F. potentiel.]
A. adj.
1. Possessing potency or power; potent, powerful, mighty, strong; commanding. Now rare.
c1485Digby Myst. (1882) ii. 360 The myght of the fadires potenciall deite. a1529Skelton Prayer to Father 2 Celestial Father, potencial God of myght. 1604Shakes. Oth. i. ii. 13 The Magnifico is much belou'd, And hath in his effect a voice potentiall As double as the Dukes. 1796Morse Amer. Geog. I. 683 The bark, when sufficiently masticated, operates as a very potential purge and emetic. 1860Mill Repr. Govt. (1865) 19/1 The nation as a whole, and every individual composing it, are without any potential voice in their own destiny.
2. Possible as opposed to actual; existing in posse or in a latent or undeveloped state, capable of coming into being or action; latent.
1398Trevisa Barth. De P.R. xix. viii. (Bodl. MS), Potencial liȝt þat is in a bodie medled and derke passeþ not to worke in dede but bi comynge of outeward liȝt. 1626Prynne Perpet. Regen. Man's Est. 262 This cannot imply an actuall or a potentiall fall from the state of grace. 1657S. Purchas Pol. Flying-Ins. i. ii. 3 The Worm or Potential Bee. 1766Blackstone Comm. II. xvi. 261 When he [a sole corporation] dies or resigns, though there is no actual owner of the land till a successor be appointed, yet there is a legal, potential ownership, subsisting in contemplation of law. 1861Kent Comm. Amer. Law (1873) II. xxxix. 468 The thing sold must have an actual or potential existence. 1872Nicholson Biol. 15 Life may remain in a dormant or ‘potential’ condition for an apparently indefinite length of time. 1897Westm. Gaz. 10 Mar. 6/2 The ships..put out under steam, running eight or nine throughout the night to avoid potential torpedoes.
3. Med. potential cautery, an agent which produces the same effects on the skin as an actual cautery or red-hot iron. So potential corrosive.
c1400Lanfranc's Cirurg. 305 He knowiþ not þe difference bitwixe a cauterie þat is clepid actuel & potencial. 1597A. M. tr. Guillemeau's Fr. Chirurg. 17 b/2 We vse nowe in these dayes potentialle corrosiues. 1612Woodall Surg. Mate Wks. (1653) 90 In which case..a potential Caustick medicament..is convenient. 1696Phillips (ed. 5), Potential Cautery..is that which is perform'd with Limestone or other Caustick Druggs. 1758J. S. tr. Le Dran's Observ. Surg. (1771) 174, I prefer the Potential Cautery, such as the Lapis Infernalis, or the Mercurial Water. 1895Syd. Soc. Lex., Potential cautery, nitrate of silver..or Potassa fusa, as distinct from the Actual cautery, or red-hot iron.
4. Gram.
a. That expresses potentiality or possibility: potential mood, a name sometimes given to the subjunctive mood, when used to express possibility; the subjunctive mood used potentially.
In French Grammar, sometimes applied to the Conditional (j'aurais, je serais, etc.).[1524Linacre De Emendata Structura Latini Sermonis (ed. Paris 1550) 30 Potentialem vocamus, quem Graeci per ἄν coniunctionem & verbum duplicis modi, alias indicatiui, alias optatiui, explicant.] 1530Palsgr. Introd. 31 Modes: every parfyte verbe hath vi, the indicatyve, imperatyve, optatyve or potenciall, the subjunctyve, the condicionall, and the infynityve. 1612Brinsley Pos. Parts (1669) 31 How know you the Potential Mood? It sheweth an ability, will, or duty to do any thing. 1704J. Harris Lex. Techn. I, Potential Mood in Grammar, is the same in form with the Subjunctive; but differs in this, That it hath always Implied in it, either Possum, Volo, or Debeo; as Roget Quis, that is, Rogare potest, a Man may ask. 1824L. Murray Eng. Gram. (ed. 5) I. ii. i. 117 That the Potential Mood should be separated from the subjunctive, is evident, from the intricacy and confusion which are produced by their being blended together, and from the distinct nature of the two moods; the former of which may be expressed without any condition, supposition, etc. 1837G. Phillips Syriac Gram. 111, The tenses, especially the future, either alone or in connection with one or more particles, in many cases express a potential, subjunctive, or hypothetical sense. 1876Mason Eng. Gram. (ed. 21) 60 To these moods [Infinitive, Indicative, Imperative, Subjunctive] many grammarians add the Potential Mood, meaning by that mood certain combinations of the so-called auxiliary verbs may, might, can, could, must, with the infinitive mood. This is objectionable. 1945Language XXI. 2 In English what may be called the potential mode of the verb is an overt category marked by the morpheme can or could. 1946[see handle v.1 1 b]. 1964P. Healey in F. W. Householder Syntactic Theory I (1972) iii. xv. 216 It will be noted that the Potential tense may occur in the Quote of the Saying sub-type.
b. With humorous play on sense 2.
1680T. Jordan London's Glory 2 [Followed by] all Lord Mayors in the Potential Mood. 1823Byron Juan xi. xxxv, By those who govern in the mood potential.
5. Physics.
a. potential function: a mathematical function or quantity by the differentiation of which the force at any point in space arising from any system of bodies, etc. can be expressed. In the case in which the system consists of separate masses, electrical charges, etc., this quantity is equal to the sum of these, each divided by its distance from the point.
Introduced in 1828, by G. Green, with special reference to electricity.
1828G. Green Applic. Math. Anal. to Electr. & Magn. in Math. Papers (1871) 9 Nearly all the attractive and repulsive forces..in nature are such, that if we consider any material point p, the effect, in a given direction, of all the forces acting upon that point, arising from any system of bodies S under consideration, will be expressed by a partial differential of a certain function of the co ordinates which serve to define the point's position in space. The consideration of this function is of great importance in many inquiries... We shall often have occasion to speak of this function, and will therefore, for abridgement, call it the potential function arising from the system S. 1882Minchin Unipl. Kinemat. 135 The function ϕ is called the potential-function of the strain, and the curves obtained by varying the constant in the equation ϕ = C are called curves of equal potential. 1931Rev. Mod. Physics III. 288 He..used several forms for the potential function; one in which the potential depended only upon central force fields..and others in which the potential was also a function of the apex angle. 1939L. Bairstow Appl. Aerodynamics (ed. 2) vii. 320 The boundary conditions to be satisfied are easily deduced; a solid boundary must be a stream-line and along it ψ must be constant or dψ/ds zero. In the case of the potential function the condition takes the form that the normal velocity, i.e. dϕ/dh must be zero. 1960Houghton & Brock Aerodynamics xi. 267 The velocity potential and the stream function are combined in a new function called the complex potential function. 1967N. M. Queen Vector Anal. vii. 66 An auxiliary function from which a given vector field V can be derived by a suitable differential operation is sometimes called a potential function for V; in particular, ϕ and A in equation (7.2) are known as the scalar and vector potentials for V.
b. potential energy: energy existing in a positional form, not as motion: see energy 6.
Introduced by Rankine in 1853, potential being opposed to actual, as in sense 2; Thomson and Tait substituted kinetic for actual, making potential energy the opposite of kinetic energy. The Latin expression vis potentialis had been used by the two Bernoullis and Euler a 1750.[1744Euler Methodus inveniendi lineas curvas, etc. 246 Quamobrem cum vir celeberrimus..Daniel Bernoulli mihi indicasset se universam vim, quae in lamina elastica incurvata insit, una quadam formula quam vim potentialem appellat complecti posse.] 1853W. Rankine Transform. Energy in Sci. Papers (1881) 203 By the occurrence of such changes, actual energy disappears, and is replaced by Potential or Latent Energy; which is measured by the product of a change of state into the resistance against which that change is made. (The vis viva of matter in motion, thermometric heat, radiant heat, light, chemical action, and electric currents, are forms of actual energy; amongst those of potential energy are those of the mechanical powers of gravitation, elasticity, chemical affinity, statical electricity, and magnetism. 1866Odling Anim. Chem. 71 We may thus render muscular force latent in a stretched bowstring, raised cannon-ball, or other instrument, for any length of time. This latent force is generally spoken of as potential energy, while the active force exertable at any moment by the flying arrow or falling ball constitutes its actual or dynamic energy. 1868Thomson & Tait Elem. Dynamics 74 The potential energy of a conservative system, in the configuration which it has at any instant, is the amount of work that its mutual forces perform during the passage of the system from any one chosen configuration to the configuration at the time referred to. 1875A. Gamgee tr. Hermann's Elem. Hum. Physiol. Introd. 1 The human body..is an organism in which, by the chemical change of its constituent parts, potential is converted into kinetic energy. 1876Tait Rec. Adv. Phys. Sc. (1885) 364 Excellent instances of potential energy are supplied by..the wound up ‘weights’ of a clock.., by gunpowder, the chemical affinities of whose constituents are called into play by a spark [etc.]. 1881Maxwell Electr. & Magn. (ed. 2) I. 16 To determine the value of the potential energy when the magnet is placed in the field of force expressed by this potential.
c. potential temperature [tr. G. potentielle temperatur (W. von Bezold 1888, in Sitzungsb. der K. Preuss. Akad. der Wissensch. zu Berlin 1190)]: the temperature that a given body of gas or liquid would have if it were brought adiabatically to a standard pressure of 1 bar or 1 atmosphere.
1891C. Abbe tr. W. von Bezold in Mechanics of Earth's Atmosphere xvi. 243 Von Helmholtz recognized the objection..and proposed that the word ‘wärmegehalt’ should be replaced by the evidently much more proper expression ‘potential temperature’. When without gain or loss of heat it is adiabatically or pseudo-adiabatically reduced to the normal pressure. 1937N. A. V. Piercy Aerodynamics i. 21 An atmosphere is stable when the potential temperature is greater, the greater the altitude. 1962W. S. von Arx Introd. Physical Oceanogr. v. 128 In the very deepest part of the ocean such as in the trenches flanking island arcs, it can be shown that the potential temperature of the water is virtually uniform from the depth of the surrounding ocean floor to the bottom of the trench, even though the actual temerature increases somewhat with depth. 1967P. Groen Waters of Sea vii. 290 At 3500 meters, where the temperature is 1·6°C, the potential temperature is only 0·3°C lower. Whereas strictly speaking the temperature is not invariable even if there is no heat exchange, the potential temperature is, if the water proceeds to other depths and is therefore subjected to a different pressure.
B. n.
†1. A potential agent, a thing that gives power. Obs. rare.
1656Blount Glossogr., Potentials, things apt to breed or give power, strength or ability.
2. That which is possible, opposed to what is actual; a possibility. Also, resources that can be used or developed; freq. preceded by a defining word.
1817Coleridge Biog. Lit. I. xii. 245 The potential works in them, even as the actual works on them! 1883A. Edersheim Life Jesus (ed. 6) I. 634 With this belief our highest thoughts of the potential for humanity..are connected. 1889J. M. Robertson Ess. Crit. Method 92 The faculty..must be held to reach its highest potential, on the side of literature, in the case of personal gift cultivated by a literary life. 1941Sun (Baltimore) 24 June 10/2 The vast armored power, mobile tactics and industrial potential of the Nazi armies have been exhibited and proved in the Low Countries, France and the Balkans. 1943Times 10 Dec. 5/3 The whole war potential of the German Reich. 1958Spectator 14 Feb. 196/1 Industrial potential has multiplied six times since currency reform. 1958Listener 27 Nov. 897/1 Mr. Cooper managed to slip the theme of indifference and its potential into this play without breaking its back. 1959Ibid. 23 July 122/2 There is thought to be enormous oil potential. 1965Ibid. 1 July 22/3 All collections have a built-in boredom potential. 1969H. MacInnes Salzburg Connection xx. 281 His record..has been excellent. His potential was high—very high. 1970Nature 26 Dec. 1248/2 Although oceans and seas cover some 360 thousand km2.., exploitation of their vast potential is only just beginning. 1978Observer (Colour Suppl.) 12 Nov. 58/4 Children without these experiences..are likely to be handicapped in terms of the development of their full potential. 1979Country Life 21 June 2047/3 This ever-perceived dark potential is surely part of the reason why the cat is the intellectuals' favourite beast.
3. Gram. Short for potential mood: see A. 4.
4. Physics.
a. Short for potential function: see A. 5 a. Hence, the amount of energy or quantity of work denoted by this, considered as a quality or condition of the matter, electricity, etc., in question. See quots. More generally, any function from which a vector field F can be derived by differentiation, esp. the scalar potential ϕ, where F = - grad ϕ, and the vector potential A, where F = curl A.
(‘Potential as the name of a function was undoubtedly introduced by Gauss in 1840’ (G. F. Becker in Amer. Jrnl. Sci. 1893, Feb. 97). [Cf. Gauss Allgem. Lehrsätze d. Quadrats d. Entfernung Wks. 1877 V. 200 Zur bequemern Handhabung..werden wir uns erlauben dieses V mit einer besonderen Benennung zu belegen, und die Grösse das Potential der Massen, worauf sie sich bezieht, nennen.])
1828G. Green On Applic. Math. Anal. etc. in Math. Papers (1871) 32 This equation is remarkable on account of its simplicity and singularity, seeing that it gives the value of the potential for any point p′, within the surface, when V , its value at the surface itself, is known, together with [etc.]. 1853Sir W. Thomson in Philos. Mag. Ser. iv. V. 288 note, The potential at any point in the neighbourhood of or within a charged body is the quantity of work that would be required to bring a unit of positive electricity from an infinite distance to that point if the given distribution of electricity remained unaltered. 1866R. M. Ferguson Electr. (1870) 277 Instead of the word tension, used with reference to the work that can be effected by a charge when openly insulated, or electro-motive force, the word potential is now used. 1867Thomson & Tait Nat. Philos. (1883) II. 29. §483 This function [the potential] was introduced for gravitation by Laplace, but the name was first given to it by Green, who may almost be said to have in 1828 created the theory, as we now have it. Ibid. §485 The Potential at any point, due to any attracting or repelling body, or distribution of matter, is the mutual potential energy between it and a unit of matter placed at that point. 1873J. C. Maxwell Treat. Electr. & Magn. II. iii. ii. 27 (heading) The Vector-Potential of Magnetic induction. 1876Preece & Sivewright Telegraphy 5 Potential implies that function of electricity which determines its motion from one point to another. And the difference of potential, which determines the amount of this motion, is called electro⁓motive force. 1879G. B. Prescott Sp. Telephone 37 The difference..of magnetic potential existing between the diaphragm and the core is increased. 1881Maxwell Electr. & Magn. I. 76 Potential, in electrical science, has the same relation to Electricity that pressure, in Hydrostatics, has to fluid, or that temperature, in Thermodynamics, has to Heat. 1881F. Jenkin Electr. 51 The effect of contact in producing or maintaining difference of potentials. 1892Pall Mall G. 4 Feb. 6/3 (Mr. Tesla's demonstration.) Currents of these extremely high potentials appear to be absolutely without effect upon the human organism. 1902Sloane Stand. Electr. Dict. (ed. 3), The magnetic potential at any point of a magnetic field expresses the work which would be done by the magnetic forces of the field on a positive unit of magnetism as it moves from that point to an infinite distance therefrom... It is the exact analogue of absolute electric potential. 1909J. G. Coffin Vector Anal. vi. 173 We obtain H = ..∇ × Q... Q is called the potential due to the current distribution q, or the vector-potential belonging to the magnetic force H... The force vector H is obtained from the vector Q in a manner analogous to the way the force vector F is obtained from the scalar V, where..F = ∇V. 1933H. B. Phillips Vector Anal. v. 102 When the potential is known the velocity can be obtained by differentiation. If a potential exists it is simpler to describe the motion by means of it rather than the velocity. 1966McGraw-Hill Encycl. Sci. & Technol. X. 540/2 If the acceleration a satisfies a relation such as..a = -grad ϕ, the ϕ is called an acceleration potential. 1971W. Hauser Introd. Princ. Electromagnetism iii. 77 Vector function F1 is a curl-less vector function... It is therefore expressible as the negative gradient of a scalar function of position. We thus set F1 = - ∇ψ(r), where the function ψ(x, y, z) is referred to as the scalar potential of F1. Ibid., The divergenceless vector function F2 is..expressible as the curl of a vector function A,F2 = ∇ × A, where A is referred to as the vector potential of F2.
attrib.1896Academy 11 Apr. 399/2 The rate of leak..was no greater when the potential difference was 500 volts than when it was 5. 1898Engineering Mag. XVI. 101 ‘High potential’ electrical heat for irons, broilers, chafing dishes, and local applications. Ibid. 104 To run an engine dynamo..to furnish high potential heat and light.
b. Any of a group of thermodynamic functions mathematically analogous to electric and gravitational potentials, viz. the Gibbs free energy G (or ζ), the Helmholtz free energy A (or F or ψ), the enthalpy H (or χ), the internal energy U (or E or ε), and the chemical potential µ.
The Gibbs and the Helmholtz functions are given respectively by G = U + PV - TS and A = U - TS, where U is the internal energy, P the pressure, V the volume, T the temperature, and S the entropy of the system. The chemical potential µi of a component i in a given phase is equal to (∂G/∂mi)P,T, where mi is the quantity of the component present in the phase and the quantities of all other components remain constant.
1878J. W. Gibbs in Trans. Connecticut Acad. Arts & Sci. III. 119 If we call a quantity µx, as defined by such an equation as (12), the potential for the substance Sz in the homogeneous mass considered, these conditions may be expressed as follows:—The potential for each component substance must be constant throughout the whole mass. Ibid. 149 If to any homogeneous mass we suppose an infinitesimal quantity of any substance to be added, the mass remaining homogeneous and its entropy and volume remaining unchanged, the increase of the energy of the mass divided by the quantity of the substance added is the potential of that substance in the mass considered... In the above definition we may evidently substitute for entropy, volume, and energy, respectively, either temperature, volume, and the function ψ; or entropy, pressure, and the function χ; or temperature, pressure, and the function ζ. 1917G. E. Gibson tr. Sackur's Textbk. Thermo-Chem. & Thermodynamics vi. 178 The component I can go spontaneously from B to A if its chemical potential in A is less than its chemical potential in B. Ibid. 179 In chemistry it is usual to take the mol of each component as the unit of mass, and we may then define the chemical potential..of the component I in the solution A as the change in the thermodynamic potential of a very large mass of A when 1 mol of the component I is added to it without changing the temperature, the pressure or the masses of the other components. 1924H. S. Taylor Treat. Physical Chem. I. ii. 67 The thermodynamic potential of all spontaneously occurring processes decreases. 1937M. W. Zemansky Heat & Thermodynamics xvii. 321 If a substance is not present in a phase, it does not follow that its chemical potential is zero. The chemical potential is a measure of the effect on the Gibbs function when a substance is introduced. 1950E. O. Hercus Elem. Thermodynamics & Statistical Mech. iv. 24 Two new thermodynamical quantities dependent only on the state of a system can be defined from the entropy. These are: Free Energy, F = U - TS. Thermodynamic Potential, G = H - TS = U + pv - TS. 1960Hall & Ibele Engin. Thermodynamics x. 183 The stability of thermodynamic systems can be examined with reference to a set of quantities known as thermodynamic potentials. 1973D. C. Kelly Thermodynamics & Statistical Physics viii. 147 The four thermodynamic potentials were invented to make thermodynamics ‘easy’. Each potential is the natural energy variable for certain classes of physical processes.
c. Special Comb.: potential barrier, a region in a field of force in which the potential is significantly higher than at points either side of it, so that a particle requires energy to pass through it; spec. that surrounding the potential well of an atomic nucleus; potential flow, flow which is irrotational and for which there therefore exists a velocity potential; potential gradient, (the rate of) change of (electrical) potential with distance; potential scattering Nuclear Physics, elastic scattering of a particle by an atomic nucleus in which the scattering cross-section varies smoothly with the energy of the incident particle (cf. resonance scattering); potential wall, a region in a field of force in which the potential increases sharply; potential well, a region in a field of force in which the potential is significantly lower than at points immediately outside it, so that a particle in it is likely to remain there unless it gains a relatively large amount of energy; spec. that in which an atomic nucleus is situated.
1929Physical Rev. XXXIII. 134 The particle in the internal region received energy sufficient to raise it over the *potential barrier. 1931G. Gamow Constitution of Atomic Nuclei ii. 37 How can such an α-particle get out from the nucleus if it has to cross on its way a potential barrier which is certainly higher than the total energy of the α-particle itself? 1966H. J. Reich et al. Theory & Applications Active Devices iii. 64 An electron encounters a potential barrier in moving from left to right across the junction. 1973V. Acosta et al. Essent. Mod. Physics xvi. 223 (heading) A beam of particles of kinetic energy E is incident on a potential barrier V>E with a width of OA = t.
1937N. A. V. Piercy Aerodynamics v. 140 Irrotational flow is often called *potential flow. 1962Walshaw & Jobson Mech. of Fluids viii. 211 ‘Potential’ flows..neglect viscous actions and merely provide a framework of reference against which the behaviour of a real fluid may be compared. 1975Sci. Amer. Nov. 85/1 An airfoil or a wing in steady motion through the air is a device by means of which circulation is created and maintained in the form of a vortex bound to the wing. This bound vortex is then superposed on the flow pattern that the wing profile would produce in an ideal fluid. The pattern is termed the potential flow.
1895A. Daniell Text-bk. Princ. Physics (ed. 3) xvi. 585 This Electric Force on Unit Quantity, ϕ = (V′ - V{pp}) {div} d, is the Potential-Slope or *Potential-Gradient. 1931Discovery July 212/1 Measurements of potential gradient have been made in balloons up to a height of nine kilometres. The gradient falls off rapidly, most of the positive charge being in the lower strata. 1963E. V. Vernon in Zepler & Punnett Electron Devices & Networks i. 25 The potential gradient along the material is due to its ohmic resistance. 1973R. Brown Electricity & Atomic Physics xii. 270 There is a potential gradient in the depletion layer, positive on the n side and negative on the p side, and this represents a potential barrier.
1937Bethe & Placzek in Physical Rev. LI. 460/2 It amounts..to a scattering cross section σ1 = 4πR2... This part may be called *potential scattering in the narrower sense. Ibid. 462/1 The total potential scattering is σpot = (σ1½ - σ3½). 1955A. E. S. Green Nuclear Physics xiii. 433 Within the category of elastic scattering we may distinguish two types of processes, namely, potential scattering and resonant scattering. 1971B. L. Cohen Concepts of Nuclear Physics xiii. 331 Between the resonances in Fig. 13–7 we see the effects of potential scattering only.
1931Proc. R. Soc. A. CXXXIII. 238 If this theory of the resonance levels is correct, it is difficult to reconcile the results of Pose, who finds quite sharp resonance levels in Al, with the results of experiments on α-particles of sufficient energy to pass over the top of the *potential wall. 1973V. Acosta et al. Essent. Mod. Physics xvi. 222 This situation may be treated in a simplified manner by using a thin potential wall—a potential barrier.
[1931G. Gamow Constitution of Atomic Nuclei i. 18 The potential..must be more or less constant inside the nucleus and increase sharply at the boundary, the distribution forming a ‘potential hole’ of the shape shown.] 1935Physical Rev. XLVII. 852/1 The positive valued parameters A and α are to be determined to fit the binding energies of the deuteron and the alpha⁓particle. Evidently A and 1/α½ are directly proportional to the depth and breadth, respectively, of the *potential well. 1952Blatt & Weisskopf Theoret. Nuclear Physics ii. 49 Even very refined experiments at low energies do not suffice to determine more than an ‘effective range’ and ‘depth’ of the potential well, leaving the detailed shape completely indeterminate. 1972DePuy & Chapman Molec. Reactions & Photochem. i. 1 Within this potential well the molecule can occupy any of a number of discrete vibrational energy levels. |