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[am-peer, am-peer] /ˈæm pɪər, æmˈpɪər/
noun, Electricity
the basic unit of electrical current in the International System of Units (SI), equivalent to one coulomb per second, formally defined to be the constant current which if maintained in two straight parallel conductors of infinite length, of negligible circular cross section, and placed one meter apart in vacuum, would produce between these conductors a force equal to 2 × 10 −7 newton per meter of length.
Abbreviation: A, amp.
Also, ampère.
1881; named after A. M. Ampère


[am-peer; French ahn-per] /ˈæm pɪər; French ɑ̃ˈpɛr/
André Marie
[ahn-drey muh-ree;; French ahn-drey ma-ree] /ˈɑn dreɪ məˈri;; French ɑ̃ˈdreɪ maˈri/ (Show IPA),
1775–1836, French physicist.
Related forms
[am-peer-ee-uh n, -per-] /æmˈpɪər i ən, -ˈpɛr-/ (Show IPA),
adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for ampere
  • Parks often base the charge of the site upon the electrical ampere hookup.
  • Busbars shall have an ampere rating not less than the overcurrent device supplying the feeder supplying the box.
  • Air-gap flux densities vs ampere-turns produced by an excitation coil for two different coil locations.
British Dictionary definitions for ampere


the basic SI unit of electric current; the constant current that, when maintained in two parallel conductors of infinite length and negligible cross section placed 1 metre apart in free space, produces a force of 2 × 10–7 newton per metre between them. 1 ampere is equivalent to 1 coulomb per second
a former unit of electric current (international ampere); the current that, when passed through a solution of silver nitrate, deposits silver at the rate of 0.001118 gram per second. 1 international ampere equals 0.999835 ampere
amp, A
Word Origin
C19: named after André Marie Ampère


/ˈæmpɛə; French ɑ̃pɛr/
André Marie (ɑ̃dre mari). 1775–1836, French physicist and mathematician, who made major discoveries in the fields of magnetism and electricity
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for ampere

1881, "the current that one volt can send through one ohm," from French ampère, named for French physicist André-Marie Ampère (1775-1836). Shortened form amp is attested from 1886.

Online Etymology Dictionary, © 2010 Douglas Harper
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ampere in Medicine

ampere am·pere (ām'pēr')
Abbr. A

  1. A unit of electric current in the meter-kilogram-second system, equal to the current that, flowing in two parallel wires one meter apart, produces a force of 2 × 10-7 newtons per meter.

  2. A unit in the International System specified as one International coulomb per second and equal to 0.999835 ampere.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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ampere in Science
The SI unit used to measure electric current. Electric current through any given cross-section (such as a cross-section of a wire) may be measured as the amount of electrical charge moving through that cross-section in one second. One ampere is equal to a flow of one coulomb per second, or a flow of 6.28 × 1018 electrons per second.
  (ām'pîr', äm-pěr')   
French mathematician and physicist who is best known for his analysis of the relationship between magnetic force and electric current. He formulated Ampère's law, which describes the strength of the magnetic field produced by the flow of energy through a conductor. The ampere unit of electric current is named for him.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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ampere in Technology

unit, electronics
(Amp, A) The unit of electrical current flow. One Amp is the current that will flow through a one-ohm resistance when one Volt DC is applied across it.

The Free On-line Dictionary of Computing, © Denis Howe 2010
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Encyclopedia Article for ampere

unit of electric current in the Systeme International d'Unites (SI), used by both scientists and technologists. Since 1948 the ampere has been defined as the constant current which, if maintained in two straight parallel conductors of infinite length of negligible circular cross section and placed one metre apart in a vacuum, would produce between these conductors a force equal to 2 10-7 newton per metre of length. Named for the 19th-century French physicist Andre-Marie Ampere, it represents a flow of one coulomb of electricity per second. A flow of one ampere is produced in a resistance of one ohm by a potential difference of one volt. See electric current.

Learn more about ampere with a free trial on
Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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