Which instrument indicates power factor in the described material?

• A. Voltmeter
• B. Ammeter
• C. Ohmmeter
• D. Wattmeter

Answer: (D)

Power factor tells how effectively current is being used and is the ratio of real power to apparent power. The wattmeter reads real power in watts. With the known voltage and current, you can compute apparent power as VI, then PF = P / (VI). So the wattmeter provides the essential real-power value needed to determine power factor, which is why it’s the instrument that indicates power factor in this context. The voltmeter, ammeter, and ohmmeter measure voltage, current, or resistance respectively, but do not directly give power factor. For example, if you have 120 V and 10 A, a wattmeter showing 960 W gives PF = 960 / (120 × 10) = 0.8.