What happens to the power factor when voltage and current are out of phase?

• A. It increases
• B. It remains constant
• C. It decreases
• D. It doubles

Answer: (C)

When voltage and current are out of phase, the power factor decreases. The power factor is a measure of how effectively electrical power is being converted into useful work output and is defined as the cosine of the phase angle between the current and voltage waveforms.

When the voltage and current are in phase (meaning they reach their peak values at the same time), the power factor is 1, which indicates that all the power is being effectively used. However, when there is a phase difference, particularly if they are out of sync, some of the power is wasted as reactive power, strictly contributing to energy that does not perform any useful work.

As the phase angle increases, the power factor, calculated as cosine of this angle, becomes smaller. This reduction in power factor signifies that the efficiency of power being utilized decreases, leading to a poorer performance in terms of energy consumption.

Thus, when voltage and current are out of phase, it leads to a decrease in the power factor, reflecting less efficiency in the system.