Watt Watt The watt (symbol: W) is a unit of power. In the International System of Units (SI) it is defined as a derived unit of 1 joule per second, and is used to quantify the rate of energy transfer. When an object's velocity is held constant at one meter per second against a constant opposing force of one newton, the rate at which work is done is 1 watt. In terms of electromagnetism, one watt is the rate at which electrical work is performed when a current of one ampere (A) flows across an electrical potential difference of one volt
2019 redefinition of SI base units the Avogadro constant, Brian Leonard of the University of Akron, writing in "Metrologia" proposed that the dalton (Da) be redefined such that , but that the unified atomic mass unit () retain its current definition based on the mass of C, ceasing to exactly equal to the dalton. This would result in the dalton and the atomic mass unit potentially differing from each other with a relative uncertainty of the order of 10. However, the draft of the ninth SI Brochure defines both the dalton (Da) and the unified atomic mass unit (u) as exactly 1/12 of the mass of