Question 359: AC fundamentals

Question

For a purely inductive or a purely capacitive circuit, the power factor is

Accepted Answer

For a purely inductive or a purely capacitive circuit, the power factor is indeed zero. That makes Option A the correct choice. Let's explain why this is the case.
In AC circuits, the power factor is defined as the cosine of the phase angle (denoted as $$ \cos(\phi) $$) between the voltage and the current. The power factor can range from -1 (which would be for a purely capacitive load with current leading the voltage by 90 degrees) to +1 (which would be for a purely resistive load with voltage and current in phase). If the power factor is zero, this means that the phase angle between the voltage and current is 90 degrees.
In a purely inductive circuit, the inductor causes the current to lag behind the voltage by 90 degrees, while in a purely capacitive circuit, the capacitor causes the current to lead the voltage by 90 degrees. In both cases, the current is out of phase with the voltage by 90 degrees, which gives us a phase angle $$ \phi = \pm90^\circ $$. The cosine of +90 degrees or -90 degrees is zero:
$$ \cos(90^\circ) = \cos(-90^\circ) = 0. $$
This means that in both cases (pure inductance or pure capacitance), there is no real power being consumed or dissipated in the circuit. Instead, power is just oscillating back and forth between the source and the reactive component (the inductor or capacitor). This oscillating power is known as reactive power, and while it is transferred to and from the source, it is not converted into heat or work. Therefore, the real power (the part of power which does work or generates heat) in a purely inductive or capacitive circuit is zero, and hence the power factor is zero.

Answer

zero

Answer

0.5

Answer

1

Answer

$$\infty$$

AC fundamentals

For a purely inductive or a purely capacitive circuit, the power factor is

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