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
Ohm applied voltages or currents; many practical resistors are linear over a useful range of currents. Non-linear resistors have a value that may vary depending on the applied voltage (or current). Where alternating current is applied to the circuit (or where the resistance value is a function of time), the relation above is true at any instant but calculation of average power over an interval of time will require integration of "instantaneous" power over that interval. Since the ohm belongs to a coherent system of units, when each of these quantities has its corresponding SI unit (watt for "P", ohm for