n. the basic *SI unit of electric current. It is equal to the current flowing through a conductor of resistance 1 ohm when a potential difference of 1 volt is applied between its ends. The formal definition of the ampere is the current that when passed through two parallel conductors of infinite length and negligible cross section, placed 1 metre apart in a vacuum, produces a force of 2 × 10?7 newton per metre between them. Symbol: A.
The international system of measurement-units used throughout the sciences. SI units, which derive from metres, kilograms, and seconds, comprise seven basic units and two supplementary ones. Among the other base units are ampere (electric current) and mole (amount of a substance at molecular level). Derived SI units include joule (energy), pascal (pressure), becquerel (activity), and newton (force). (See APPENDIX 6: MEASUREMENTS IN MEDICINE.)... si units
n. the *SI unit of work or energy, equal to the work done when the point of application of a force of 1 newton is displaced through a distance of 1 metre in the direction of the force. In electrical terms the joule is the work done per second when a current of 1 ampere flows through a resistance of 1 ohm. Symbol: J. See also calorie.... joule
n. short for milliampere: one thousandth of an *ampere (10?3 A; symbol: mA). In radiography, the mA setting on an X-ray machine determines the number of X-ray photons produced per second. The setting is important to obtain appropriate exposure and varies with body size (among other factors). See also kilovolt.... milliamp
n. the *SI unit of power, equal to 1 joule per second. In electrical terms it is the energy expended per second when a current of 1 ampere flows between two points on a conductor between which there is a potential difference of 1 volt. 1 watt = 107 ergs per second. Symbol: W.... watt
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