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ampere Electr.
(‖ ɑ̃ːˈpɛr, ˈæmpɛə(r))
Also ampère.
[a. Ampère, name of a Fr. electrician; a designation adopted by the Paris Electric Congress in 1881.]
(See quot. 1963). ampere-hour, the quantity of electricity equal to a current of one ampere flowing for one hour; abbrev. Ah; ampere-turn, a unit of magneto-motive force, expressed as the product of the number of turns in a coil and the current in amperes; abbrev. A.T.
1881Q. Rev. Oct. 457 The unit of current is called the ‘Ampère.’ It is the current that one volt can send through one ohm. 1883A. Grey in Nature XXVII. 321 The current flowing in a wire of resistance one ohm, between the two ends of which a difference of potentials of one volt is maintained, has been adopted as the practical unit of current and called one ampere. 1884J. T. Sprague Electricity 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. 1885Electrician 27 Nov. 49/1 Secondary cells..giving 280 ampere hours. 1912G. Kapp Electricity vi. 166 The excitation produced by a coil may be conveniently expressed by the product of amperes and turns, or ‘ampere-turns’. 1919R. Stanley Wireless Telegr. I. 452 A proper check..of the number of ampere-hours' charge and discharge. 1963Jerrard & McNeill Dict. Sci. Units 17 The 9th Meeting of the International Weights and Measures Congress in 1948 defined the ampere as the intensity of the constant current which, when maintained in two parallel straight conductors of infinite length and of negligible cross section placed one metre apart in a vacuum, produced between them a force equal to 2 × 10-7 M.K.S. units of force per metre length. This unit, known as the absolute ampere, replaced the international ampere which had been defined in 1908.
Sense in Dict. becomes 2. Add: 1. Used in the possessive to designate various laws of electromagnetism deduced or derived by Ampère, esp. (a) the law relating the current in a conductor to the magnetic flux density it produces; also, the theorem derived from this, which states that the line integral of magnetic flux density around any closed path is proportional to the net current passing through the enclosed area; (b) the mnemonic rule that the lines of magnetic force generated by a current in a conductor would appear to run clockwise to an observer looking in the direction of the current.
1861Phil. Mag. XXI. 248 Now, according to Ampère's well-known law of angular currents, the two currents will repel each other. 1862Ibid. XXIII. 142 When the battery was not too strongly charged..the bullets..were seen to approach each other..and gave a confirmation of Ampère's law at once simple and direct. 1884S. 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. 1903Gee & Kinzbrunner tr. Rosenberg's Electr. Engin. ii. 44 ‘If we imagine a man swimming in the wire with the electric current and so as always to face the needle, then the north pole will be deflected to the left hand of the swimmer.’ This rule is called Ampère's Rule. 1953E. R. Peck Electr. & Magn. vii. 215 Equation (7.67) is a statement of Ampère's circuital law. We may write it more briefly.. cB·dl = µ0 Ic . 1966McGraw-Hill Encycl. Sci. & Technol. II. 246/2 The field near a straight conductor can be found by application of Ampere's law. 1984D. C. Giancoli Gen. Physics xxix. 564 We now use Ampère's law to determine the magnetic field inside a very long..closely packed solenoid.
[2.] Add to def.: With lower-case-initial. |