Discussion
In an AC circuit, the power factor is the cosine of the :
Answer: C
The power factor is the cosine of the phase angle.
In an AC circuit the current and voltage have the same frequency but may be shifted in time. The phase angle \(\phi\) is the angle between the voltage and current phasors, and the real power is
\[ P = V_{rms} I_{rms} \cos\phi \]
so \(\cos\phi\) is the fraction of the apparent power that does useful work. It equals 1 for a purely resistive load and falls towards zero as the load becomes purely inductive or capacitive.
The voltage angle and current angle on their own depend on the arbitrary reference chosen; only their difference matters. 'Resistance angle' is not a defined quantity, although the impedance angle is equal to \(\phi\).
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