The power losses in an AC-driven circuit depend not only upon the rms voltages and currents in the circuit, but also the power factor, cos[itex]\phi[/itex], where [itex]\phi[/itex] is the phase difference between the current and the applied alternating voltage.(adsbygoogle = window.adsbygoogle || []).push({});

In purely capacitive and purely inductive circuits, the phase difference is 90°, and so, the power factor is:

cos(90°) = 0.

Which means there is no power transferred from the alternating voltage source to any part of the circuit.

But how is that possible? The alternating voltage produced by a dynamo (or nay other AC source), during every cycle involve new energy inputs (the rotating armature) every cycle. So, there should be an energy buildup somewhere....

The energy seen in the form of voltage in one direction can't go back to the ac source during the time the voltage decays, because then there would be a buildup of energy in the source - the energy that is returning to it during voltage decay, and the new energy that produces the voltage of the next half of the cycle.

There seems to be a contradiction....

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# Energy in AC-Driven Purely Inductive/Capacitive Circuit

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