Final answer:
A negative wattmeter reading in a 2-wattmeter method indicates the load has a leading power factor, which means the current leads the voltage, typically due to capacitive characteristics of the load. Correcting the power factor to unity involves adding a capacitor to adjust the phase difference. Power factor represents the efficiency of power use in a circuit.
Step-by-step explanation:
If one wattmeter reading is negative in the 2-wattmeter method, this typically indicates that the load has a leading power factor. This situation occurs when the current leads the voltage, which is characteristic of a circuit that has a capacitive nature. In contrast, a lagging power factor would imply that the current lags behind the voltage, usually due to an inductive load. A power factor of 1 (unity) would mean that the voltage and current are in phase, which would not result in a negative reading on any wattmeter. Therefore, the correct answer is B. The load has a leading power factor.
In the context of improving power efficiency, it's important to understand that a high power factor is desirable as it means less power is being wasted. For a circuit where the voltage is lagging the current with a power factor of 0.50, adding a capacitor in series would help to correct the phase difference, raising the power factor toward unity. If a motor has a power factor significantly less than 1, it implies that it's consuming more reactive power, and improving the power factor would make the motor more efficient rather than just increasing the voltage input.
The average power delivered in an AC circuit such as an RLC circuit is given by the formula Pave = Irms Vrms cos φ, where φ is the phase angle and cos φ is known as the power factor. For a purely resistive circuit, or an RLC circuit at resonance, the power factor would be at its maximum of 1.