How is power factor defined in an electrical circuit?

Power factor is a critical concept in electrical engineering, particularly concerning alternating current (AC) circuits. It is defined as the ratio of real power (measured in watts) to apparent power (measured in volt-amperes). Real power represents the actual power consumed by electrical devices to perform useful work, such as lighting a bulb or turning a motor. Apparent power, on the other hand, includes both real power and reactive power, which is the power that oscillates between the source and the load without being consumed. Thus, the power factor quantifies how efficiently electrical power is being converted into useful work.

A power factor of 1 (or 100%) indicates that all the power is being effectively converted into work, while a lower power factor signifies that a portion of the power is being wasted, often due to reactance in the circuit. Understanding power factor is essential for managing energy costs and improving the efficiency of electrical systems.