AC Power & Power Factor Practice Test

AC circuits deal with three kinds of power. Real power (watts, W) does actual work — heat, light, motion. Reactive power (VARs) is power that inductors and capacitors trade back and forth without doing useful work. Apparent power (volt-amps, VA) is the total the source supplies: S = V × I. Power factor (PF = P / S) tells you how much of that apparent power is actually useful. Motors and other inductive loads pull power factor down ("lagging"); capacitors can push it back up. A low power factor means more current for the same useful work — bigger wires, bigger bills.