Power is the rate at which energy is supplied or transferred, or, equivalently, the rate at which work is done, dW/dt. If the force that is doing the work is constant, then the power, P = F ds/dt , i.e., P = Fv.


The SI unit of power is the watt (W); it is equivalent to the joule per second (J s-1) or kg m2 s-3. Power has dimensions [M]1 [L]2 [T]-3.


While mechanical power may be derived as a product of a force and a velocity (linear or angular), the electrical power utilized in a circuit is a product of the potential drop and the current flowing in it (volts × amperes = watts). Where the electrical supply is alternating, the root-mean-square (rms) value of the voltage must be used.