How is power factor defined in an AC circuit?

Power factor in an AC circuit is defined as the ratio of real power to apparent power. Real power, measured in watts, represents the actual power consumed by a circuit to perform work, such as lighting a bulb or running a motor. Apparent power, measured in volt-amperes (VA), is the product of the total voltage and total current in the circuit, representing the total power flowing through the circuit.

By calculating the power factor as the ratio of these two types of power, one can gauge how efficiently the electrical power is being converted into useful work. A power factor of 1 (or 100%) indicates that all the power supplied is being used effectively, while a lower power factor suggests that some power is wasted due to reactive components, like inductors or capacitors, which generate magnetic and electric fields but do not contribute directly to work.

Understanding power factor is crucial for designing and operating electrical systems efficiently, as it can affect everything from billing by utilities to the performance of electrical equipment.