Active Power and Reactive Power
Let us consider a single phase power circuit in which current lags behind the voltage by an angle φ.
Let the instantaneous electric potential difference v = Vm.sinωt
Then the instantaneous current can be expressed as i = Im. sin(ωt - φ).
Where, Vm and Im are the maximum values of sinusoidally varying electric potential difference and current respectively.
The instantaneous power of the circuit is given by
