What is the formula for Reactive Power (Q) in a single phase AC circuit?

In a single-phase AC circuit, reactive power (Q) represents the power stored and then released by inductors and capacitors in the circuit. The formula for reactive power illustrates this relationship through the voltage and current and their phase difference.

The correct formula, which states that reactive power is equal to the product of the voltage (Vt) and the current (It) multiplied by the sine of the phase angle (θ), accurately captures the essence of how reactive power is calculated. The sine function is crucial here because reactive power is specifically associated with the reactive components (inductance and capacitance) in an AC circuit. This means that reactive power rises with an increase in the phase difference between the voltage and the current, which is represented by the sine of the angle.

The phase angle indicates how much the current lags or leads the voltage due to reactive elements in the circuit, and the sine of this angle shows that reactive power has a maximum value when the phase angle is 90 degrees (where the circuit is purely reactive).

Understanding this formula is essential in analyzing AC circuits, especially in power system studies, as it helps in managing voltage stability and power quality by considering not just the active power consumed, but also the reactive power which can impact