Which formula is used to calculate the power factor in an AC circuit?

The power factor in an AC circuit is a measure of how effectively the electrical power is being converted into useful work output. It is defined as the ratio of true power, which performs actual work, to apparent power, which is the product of the current and voltage in the circuit. The formula for the power factor is therefore true power divided by apparent power.

This calculation is essential because a power factor close to 1 indicates efficient utilization of electrical power, while a low power factor suggests that much of the power is reactive and not performing useful work, leading to inefficiencies in the system. The other provided formulas do not accurately represent the relationship necessary to compute the power factor. The correct formulation helps in understanding the efficiency of energy usage in AC systems and is crucial for electrical engineering applications such as load calculations and power system optimization.