We know that in a direct current circuit, the power is given by the product of the applied voltage ‘V’ and the current ‘I’,
PDC = VxI watt. But in the case of the alternating current circuit, power P = V x I cosΦ
where cosΦ = The phase difference between the applied voltage ‘V’ and the circuit current I. This power in AC is given the true or Active Power. The factor cosΦ is called the power factor of the circuit.
So, the power factor can be defined as follows:
i. It is the cosine of the angle between the applied voltage and the circuit current.
ii. It is the ratio of the true power to the apparent power.
∴ Power factor cosΦ = VICosΦ/VI
iii. It is the ratio of the resistance of the circuit to the impedance of the same circuit.
∴ cosΦ = resistance/inpedance = R/Z
Power factor = 1/’Q’ factor of a coil
By knowing the power factor of the circuit, we can understand whether the circuit is inductive or capacitive. In an inductive circuit, the circuit current lags the applied voltage and in a capacitive circuit, the circuit current leads the applied voltage.