Power in Pure resistive circuits:

The voltage and current in a pure resistive circuit are in phase and may be respectively represented by

v = Vm sin wt

and i = Im sin wt

The instantaneous power is given by

P = vi

= Vm Im sin² wt

=(1/2) Vm lm (1-cos 2wt)

The active power is given by

The power waveform is positive throughout the cycle. This is because voltage and current are in phase. The power flows only in one direction. It is consumed in R and appears in the form of heat.

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