# power

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 m^{2} 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.