AC power

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This article deals with power in AC systems. See Mains electricity for information on utility-supplied AC power.

Usually hidden from the unaided eye, the blinking of (non-incandescent) lighting powered by AC mains is revealed in this motion-blurred long exposure of city lights. Light is emitted twice each cycle.

Power is defined as the rate of flow of energy past a given point. In alternating current circuits, energy storage elements such as inductance and capacitance may result in periodic reversals of the direction of energy flow. The portion of power flow that, averaged over a complete cycle of the AC waveform, results in net transfer of energy in one direction is known as real power. The portion of power flow due to stored energy, which returns to the source in each cycle, is known as reactive power.

Contents [hide] 1 Real, reactive, and apparent power 2 Power factor 3 Reactive power flow 4 Unbalanced polyphase systems 5 Basic calculations using real numbers 6 Multiple frequency systems 7 References 8 See also