Power Factor

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).

Step 1: Calculate the total reactance.
The total reactance of the circuit is the difference between the inductive reactance and the capacitive reactance:
Step 2: Calculate the total impedance.
The total impedance of the circuit is given by:
Step 3: Calculate the power factor.
The power factor is the cosine of the phase angle , where: Since the inductive reactance is greater than the capacitive reactance, the power factor is lagging.
Step 4: Conclusion.
Thus, the overall power factor is lagging, which corresponds to option (D).