The average power dissipated in a purely inductive or purely capacitive AC circuit over a complete cycle is
Correct answer: B. zero, because energy is stored and returned each quarter cycle
- 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.
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About AC Through Resistor, Capacitor and Inductor
Alternating current through a resistor, capacitor and inductor involves phase relationships between voltage and current, reactance, impedance and energy transfer. A resistor keeps voltage and current in phase, while a capacitor and inductor produce opposite phase shifts, a distinction used in circuit diagrams and numerical calculations.
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