Question

In the measurement of power consumed by a three-phase balanced inductive load using two-wattmeter method, one of the wattmeters \( W_2 \) shows zero reading. The load power factor is

• A. zero lagging
• B. unity
• C. 0.5 leading
• D. 0.5 lagging

Hint:

If one of the wattmeters in the two-wattmeter method shows zero reading, the power factor is unity, indicating a purely resistive load.

Answer 1

The Correct Option is B

Step 1: Analyze the condition of two-wattmeter method.
In the two-wattmeter method for a balanced three-phase load, if one wattmeter reads zero, the power factor is unity. This happens when the load is purely resistive.
Step 2: Conclusion.
Thus, when one wattmeter reads zero, the power factor is unity, corresponding to option (B).