In any A.C. circuit always

Question

Examoogle · Accepted Answer

apparent power is more than actual power

Explanation: In an AC circuit, the apparent power ($S$) is the product of RMS voltage and RMS current, while the actual (real) power ($P$) is the portion that does useful work. Because the power factor ($cos\phi$) is always less than or equal to 1, the apparent power is always greater than or equal to the actual power.

Working Principle: The relationship between these powers is defined by the Power Triangle where $S^2 = P^2 + Q^2$. Since $P = S \cos\phi$, and $0 \le \cos\phi \le 1$, it follows that $P \le S$. The only case where $P = S$ is at unity power factor ($\phi = 0$°), where reactive power $Q = 0$.

Key Formulas: $S = V_{rms} \cdot I_{rms}$ — Apparent Power in VA; $P = S \cdot \cos\phi$ — Actual Power in Watts; $S = \sqrt{P^2 + Q^2}$ — Power Triangle relationship

Key Points: Apparent power represents the total capacity of the circuit.; Real power represents the energy dissipated as heat or work.; Reactive power represents the energy oscillating between source and load.; The ratio $P/S$ is defined as the Power Factor.

Advantages: Provides a clear distinction between useful and stored energy; Essential for sizing electrical equipment and cable rating

Disadvantages: High reactive power leads to poor voltage regulation; Increased transmission losses in conductors

Applications: Transformer rating design; Power factor correction units; AC motor load calculations

Additional Info: Option B and D are incorrect because reactive power is a component of the apparent power and cannot exceed it.. Option C is incorrect because real power cannot exceed the total apparent power in a passive circuit.

Answer: A is correct — The apparent power (VA) is the hypotenuse of the power triangle, making it always greater than or equal to the actual power (W).

Exam Tip: Remember that in a pure resistive circuit, power factor = 1, meaning apparent power equals actual power; in all other cases, apparent power remains strictly greater.

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