Question

Given below are two statements:
Statement (I): Power factor is Not a measure of efficiency
Statement (II): If a load draws Reactive Power, the power factor is said to be 'lagging'
In light of the above statements, choose the most appropriate answer from the options given below.

• A. Both Statement (I) and Statement (II) are true.
• B. Both Statement (I) and Statement (II) are false.
• C. Statement (I) is true but Statement (II) is false.
• D. Statement (I) is false but Statement (II) is true.

Hint:

To remember this:
- Inductive load \(\rightarrow\) Absorbs Reactive Power \(\rightarrow\) Current lags Voltage \(\rightarrow\) Lagging Power Factor.
- Capacitive load \(\rightarrow\) Generates/Supplies Reactive Power \(\rightarrow\) Current leads Voltage \(\rightarrow\) Leading Power Factor.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Power factor and efficiency are two distinct, independent parameters used to characterize the performance of AC electrical systems and equipment. Understanding their physical meanings is necessary for proper system analysis.

Step 2: Detailed Explanation:
Let us evaluate each statement:

Statement (I): Power factor is defined as the ratio of real power (\(P\), measured in Watts) to the apparent power (\(S\), measured in Volt-Amperes) delivered to a system: \[ \text{Power Factor} = \frac{P}{S} = \cos\phi \] This describes how effectively the alternating current is synchronized with the voltage to transfer energy.
Efficiency (\(\eta\)) is defined as the ratio of useful output work/power to the total input power: \[ \eta = \frac{P_{\text{out}}}{P_{\text{in}}} \times 100\% \] An electrical system or motor can operate at a high power factor but have low efficiency due to significant thermal, frictional, or magnetic core losses. Thus, power factor is not a measure of efficiency. Statement (I) istrue.

Statement (II): Inductive loads (such as electric motors, transformers, and chokes) require a magnetic field to operate.
These loads continuously absorb reactive power (\(Q\)) from the grid to sustain their magnetic fields, causing the alternating current waveform to shift and lag behind the voltage waveform by a phase angle \(\phi\).
By convention, when the current waveform lags the voltage waveform, the system's power factor is designated as "lagging." Statement (II) istrue.
Since both Statement (I) and Statement (II) are true, Option (A) is the correct choice.

Step 3: Final Answer:
Both Statement (I) and Statement (II) are true, which corresponds to Option (A).