单词 | ampere |
释义 | amperen. I. In the genitive. 1. Designating various laws of electromagnetism derived by or attributed to Ampère, as Ampere's law, Ampere's rule, etc.; esp. (a) the theorem that the integral of a magnetic field along a closed path is proportional to the current enclosed by the path; (b) a rule for finding the direction of the magnetic field produced by a current flowing through a wire; = right-hand rule n. (a) at right hand n. and adj. Compounds. ΘΚΠ the world > matter > physics > electromagnetic radiation > electricity > electrically induced magnetism > [noun] > theory or law of ampere1846 1846 E. West tr. C. F. Peschel Elem. Physics III. 207 All the mutual action of magnets and electric currents..are explicable, according to Ampère's law [Ger. nach dem Ampère'schen Gesetze] of the influence of electric currents on each other. 1884 S. P. Thompson Dynamo-electr. Machinery ii. 7 A more usual rule for remembering the direction of the induced currents is the following adaptation from Ampère's well-known rule. 1953 E. R. Peck Electr. & Magnetism vii. 215 Equation (7.67) is a statement of Ampère's circuital law. 2013 N. Giordano College Physics (ed. 2) II. xx. 688 The mathematics of Ampère's law is manageable when one can find a path along which the magnetic field is constant. II. Simple uses. 2. A unit of electrical current first introduced in the centimetre-gram-second system of units and now one of the base units in the International System of Units. Symbol A.The ampere was originally defined as the amount of current that, during one second and when the electromotive force is one volt, passes through a conductor whose resistance is one ohm. A second definition was introduced at the 1893 International Conference of Electricians, in which the ampere was taken as the unvarying current that would deposit 0.001118000 grams of silver per second from a solution of silver nitrate in water. This quantity became known as the international ampere, while that described in the original definition was called the absolute ampere.The unreliability of measurements made using the international ampere led to its abandonment at the 1948 General Conference on Weights and Measures, and the ampere was once again redefined. Under this new definition, the ampere was set as the constant current that would produce a force of 2 × 10−7 newtons per metre of length in two parallel conductors of infinite length and negligible cross-section placed one metre apart in a vacuum. This became the standard definition of the ampere until 2018, when the General Conference on Weights and Measures agreed that it would, from May of the following year, be redefined as the quantity of electrical current for which the value of the elementary charge is exactly 1.602176634 × 10−19. ΘΚΠ the world > matter > physics > electromagnetic radiation > electricity > electric current > [noun] > unit of measurement ampere1881 amp1882 milliampere1885 kilampere1892 mA1896 kVA1905 kilovolt-ampere1909 microamp1923 milliamp1923 abampere1930 1881 Q. Rev. Oct. 457 The unit of current is called the ‘Ampère.’ It is the current that one volt can send through one ohm. 1919 Pop. Sci. Monthly May 104/2 The usual amount of current used is thirty amperes. 1939 Electr. Engin. 58 80/1 It may be inferred that the mean international ampere is 0.99988 absolute ampere. 2006 A. Britton American 252 It would be necessary to check the current moving over each detonator, because he knew that a single cap would require between 2 and 10 amperes to function correctly. Compounds ampere-hour n. the quantity of electric charge equal to the charge carried by a current of one ampere during one hour, equal to 3600 coulombs of electric charge; symbol Ah.Ampere-hours are frequently used to measure the capacity of batteries. ΘΚΠ the world > matter > physics > electromagnetic radiation > electricity > electric current > [noun] > unit of measurement > timed quantity ampere-hour1883 1883 Jrnl. Soc. Arts 16 Apr. 500/1 The ampère-hour is another way of saying 3,600 coulombs of quantity of electricity supplied. 1958 Pop. Sci. Feb. 176/1 Since a 12-volt battery has only about half the ampere-hour reserve, won't it quit sooner than a six-volt? 2014 K. Pickerill Today's Technician (ed. 6) 104 The battery is rated at 5 × 20 = 100 ampere-hours. ampere-turn n. a unit of magnetomotive force in the metre-kilogram-second system of units, equal to the force produced by a current of one ampere flowing through one complete turn of a coil; symbol At. ΘΚΠ the world > matter > physics > electromagnetic radiation > electricity > electrically induced magnetism > electromagnetic induction > [noun] > magnetomotive force > unit of ampere-turn1884 gilbert1891 1884 J. T. Sprague Electr. (ed. 2) xii. 526 To equally magnetize different sized cores, the ‘ampere-turns’ must be in the proportion of the square root of the cube of the diameters. 1946 Pop. Mech. Mar. 220/2 Next step is to determine the number of ampere-turns required to give the desired pull. 2017 Nucl. Instruments & Methods in Physics Res. B. 406 244/2 Due to the highly saturated iron, the required Ampere-turns of the coils are very high. This entry has been updated (OED Third Edition, June 2019; most recently modified version published online December 2021). < n.1846 |
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