# Dictionary Definition

ampere

### Noun

1 a former unit of electric current (slightly smaller than the SI ampere) [syn: international ampere]
2 the basic unit of electric current adopted under the Systeme International d'Unites; "a typical household circuit carries 15 to 50 amps" [syn: amp, A]

# User Contributed Dictionary

## English

ampère, amp, A

### Etymology

Named after the French phyicist Ampère.

### Noun

ampere (plural amperes)
1. a unit of electrical current, the standard base unit in the International System of Units. Abbreviation: amp, Symbol: A
Definition: ''The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 metre apart in vacuum, would produce between these conductors a force equal to 2 x 10–7 newton per metre of length.'' (The International Bureau of Weights and Measures)

#### Translations

• Croatian: amper
• Finnish: ampeeri
• French: ampère
• German: Ampere
• Greek: αμπέρ (ambér)
• Italian: ampere (p: ampere)
• Polish: amper
• Russian: ампер (ampér)
• Swedish: ampere

ampere m inv

# Extensive Definition

The ampere, in practice often shortened to amp, (symbol: A) is a unit of electric current, or amount of electric charge per second. The ampere is an SI base unit, and is named after André-Marie Ampère, one of the main discoverers of electromagnetism.

## Definition

The ampere is a constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross section, and placed 1 metre apart in a vacuum, would produce between these conductors a force equal to 2×10–7 newton per metre of length. For a description of this force law, see Serway. See also Ampère's force law. The ampere is a base unit, along with the metre, kelvin, second, mole, candela and the kilogram: it is defined without reference to the quantity of electric charge.
The unit of charge, the coulomb, is defined to be the amount of charge displaced by a one ampere current per unit time of one second. Conversely, an ampere is one coulomb of charge going past a given point in the duration of one second; that is, in general, charge Q is determined by steady current I flowing per unit time t as:
Q=It \!\

## Realization

The ampere is most accurately realized using a watt balance, but is in practice maintained via Ohm's Law from the units of EMF and resistance, the volt and the ohm, since the latter two can be tied to physical phenomena that are relatively easy to reproduce, the Josephson junction and the quantum Hall effect, respectively. The official realization of a standard ampere is discussed in NIST Special publication 330 Barry N Taylor (editor) Appendix 2, p. 56.

## Proposed future definition

Since a coulomb is approximately equal to 6.24150948×1018 elementary charges, one ampere is approximately equivalent to 6.24150948×1018 elementary charges, such as electrons, moving past a boundary in one second.
As with other SI base units, there have been proposals to redefine the kilogram in such a way as to define some presently measured physical constants to fixed values. One proposed definition of the kilogram is:
The kilogram is the mass which would be accelerated at precisely 2×10-7 m/s2 if subjected to the per metre force between two straight parallel conductors of infinite length, of negligible circular cross section, placed 1 metre apart in vacuum, through which flow a constant current of exactly 6 241 509 479 607 717 888 elementary charges per second. This redefinition of the kilogram has the effect of fixing the elementary charge to be e = 1.60217653 C and would result in a functionally equivalent definition for the coulomb as being the sum of exactly 6 241 509 479 607 717 888 elementary charges and the ampere as being the electrical current of exactly 6 241 509 479 607 717 888 elementary charges per second. This is consistent with the current 2002 CODATA value for the elementary charge which is 1.60217653×10-19 ± 0.00000014×10-19 C.

### CIPM recommendation

International Committee for Weights and Measures (CIPM) Recommendation 1 (CI-2005): Preparative steps towards new definitions of the kilogram, the ampere, the kelvin and the mole in terms of fundamental constants
The International Committee for Weights and Measures (CIPM),
• approve in principle the preparation of new definitions and mises en pratique of the kilogram, the ampere and the kelvin so that if the results of experimental measurements over the next few years are indeed acceptable, all having been agreed with the various Consultative Committees and other relevant bodies, the CIPM can prepare proposals to be put to Member States of the Metre Convention in time for possible adoption by the 24th CGPM in 2011;
• give consideration to the possibility of redefining, at the same time, the mole in terms of a fixed value of the Avogadro constant;
• prepare a Draft Resolution that may be put to the 23rd CGPM in 2007 to alert Member States to these activities;

## References

ampere in Arabic: أمبير
ampere in Asturian: Amperiu
ampere in Belarusian: Ампер
ampere in Belarusian (Tarashkevitsa): Ампэр
ampere in Bengali: অ্যাম্পিয়ার
ampere in Bosnian: Amper
ampere in Breton: Amper
ampere in Bulgarian: Ампер
ampere in Catalan: Ampere
ampere in Czech: Ampér
ampere in Danish: Ampere
ampere in German: Ampere
ampere in Estonian: Amper
ampere in Modern Greek (1453-): Αμπέρ (μονάδα μέτρησης)
ampere in Spanish: Amperio
ampere in Esperanto: Ampero
ampere in Basque: Anpere
ampere in Persian: آمپر (یکا)
ampere in French: Ampère (unité)
ampere in Friulian: Ampere
ampere in Irish: Aimpéar
ampere in Galician: Ampere
ampere in Korean: 암페어
ampere in Hindi: एम्पीयर
ampere in Croatian: Amper
ampere in Indonesian: Ampere
ampere in Icelandic: Amper
ampere in Italian: Ampere
ampere in Hebrew: אמפר
ampere in Kazakh: Ампер (өлшем бірлік)
ampere in Swahili (macrolanguage): Ampea
ampere in Kurdish: Ampère
ampere in Latvian: Ampērs
ampere in Luxembourgish: Ampere (Eenheet)
ampere in Lithuanian: Amperas
ampere in Hungarian: Amper
ampere in Marathi: अँपियर
ampere in Malay (macrolanguage): Ampere
ampere in Dutch: Ampère
ampere in Japanese: アンペア
ampere in Norwegian: Ampere
ampere in Norwegian Nynorsk: Ampere
ampere in Low German: Ampere
ampere in Polish: Amper
ampere in Portuguese: Ampère
ampere in Romanian: Amper
ampere in Russian: Ампер
ampere in Albanian: Amperimetri
ampere in Simple English: Ampere
ampere in Slovak: Ampér
ampere in Slovenian: Amper
ampere in Serbian: Ампер
ampere in Serbo-Croatian: Amper
ampere in Finnish: Ampeeri
ampere in Swedish: Ampere
ampere in Thai: แอมแปร์
ampere in Vietnamese: Ampe
ampere in Turkish: Amper
ampere in Ukrainian: Ампер
ampere in Chinese: 安培