The average power dissipated in a purely inductive or purely capacitive AC circuit over a complete cycle is
- A. maximum
- B. zero, because energy is stored and returned each quarter cycle
- C. equal to VI
- D. half of VI
Explanation
With a 90 degree phase difference the power is positive for one quarter cycle and equally negative for the next, so the net energy transfer over a full cycle is zero: the component stores energy in its field and returns it to the source. Only resistance actually dissipates energy as heat. This is why the power factor, cos of the phase angle, is zero for a pure reactance.