___ is the ratio of the actual power delivered by a load divided by the input power required by the load to operate.

• A. True power
• B. Phase shift
• C. Reactive power
• D. Power factor

Answer: (D)

Power factor describes how effectively the current drawn from the source is converted into useful work. It is the ratio of real (actual) power that does work to the apparent power supplied by the source. Real power, measured in watts, is the portion that actually does useful work, while apparent power, measured in volt-amperes, represents the total power the system must handle (voltage times current). The power factor, which equals real power divided by apparent power, tells you what fraction of the input power is being effectively used. When voltage and current are in perfect phase, the power factor is 1, meaning all the supplied power does work. If there’s a phase difference due to reactive components, the power factor drops below 1, indicating some power is tied up in reactive effects and does not contribute to useful work. This is why power factor is the correct term for the described ratio.