In a circuit low reactive power compared to true power indicates

Question

Examoogle · Accepted Answer

High power factor

Explanation: In an AC electrical circuit, the power factor ($\cos \phi$) is defined as the ratio of true power ($P$) to apparent power ($S$). When reactive power ($Q$) is low relative to true power, the phase angle $\phi$ is small, leading to a high power factor, ideally approaching unity.

Working Principle: The Power Triangle relationship is governed by the vector sum of real power and reactive power: $S = \sqrt{P^2 + Q^2}$. If $Q 	o 0$, then $S 	o P$, and since $\cos \phi = \frac{P}{S}$, the power factor increases toward 1. A low $Q$ implies the load is primarily resistive, requiring less magnetizing current from the supply.

Key Formulas: $P.F. = \cos \phi = \frac{P}{S}$ — Basic definition of Power Factor; $Q = P 	an \phi$ — Relationship between Reactive and True power

Key Points: Unity power factor implies zero reactive power consumption.; Higher power factor reduces the current drawn for the same amount of real power transfer.; Electrical systems are typically designed to maximize power factor to minimize $I^2R$ losses.

Advantages: Reduced transmission line losses; Increased voltage regulation at load end

Disadvantages: None regarding the power factor itself; however, maintaining high power factor often requires additional hardware like capacitor banks.

Applications: Industrial motor drives; Power distribution grids

Additional Info: A power factor of 1.0 (unity) is the theoretical ideal for AC systems.. Option A is incorrect because low power factor results from high reactive power relative to true power.

Answer: B is correct — A low ratio of reactive power to true power results in a phase angle $\phi$ close to zero, yielding a high power factor approaching unity.

Exam Tip: Always remember that increasing the power factor (via capacitors) decreases the current for a fixed load, which directly reduces copper losses ($I^2R$) in the line.

Related Questions

Discussion (0)