Watt within the then-existing system of practical units as "the power conveyed by a current of an Ampère through the difference of potential of a Volt." In October 1908, at the International Conference on Electric Units and Standards in London, so-called "international" definitions were established for practical electrical units. Siemens' definition was adopted as the "international" watt. (Also used: 1 ampere x 1 ohm.) The watt was defined as equal to 10 units of power in the "practical system" of units. The "international units" were dominant from 1909 until 1948. After the 9th General Conference on Weights and Measures in 1948,
Ampere-turn Ampere-turn The ampere-turn (At) is the MKS (Metres, Kilograms, Seconds) unit of magnetomotive force (MMF), represented by a direct current of one ampere flowing in a single-turn loop in a vacuum. "Turns" refers to the winding number of an electrical conductor composing an inductor. For example, a current of 2 A flowing through a coil of 10 turns produces an MMF of 20 At. By maintaining the same current and increasing the number of loops or turns of the coil, the strength of the magnetic field increases because each loop or turn of the coil sets up its own magnetic