Which statement best describes power factor?

Which statement best describes power factor?

• A. PF = cosφ; indicates portion of current delivering real work; low PF increases losses and penalties.
• B. PF = sinφ; indicates phase shift
• C. PF = P/Q; indicates efficiency
• D. PF = V/I; indicates system voltage

Answer: (A)

Power factor describes how effectively electrical power is converted into useful work in an AC circuit. It is the cosine of the phase angle between voltage and current, reflecting the portion of the current that actually drives real power. When the angle is small, most of the current does useful work, so the power factor is near 1. When the angle is large, more current is needed for the same real power, increasing conductor losses (I^2R) and potentially utility penalties for poor PF. This statement is correct because PF = cos φ, which directly links the real power portion to the total apparent power. The ideas that PF equals sin φ, equals P/Q, or equals V/I mix up different electrical quantities: sin φ relates to reactive vs. apparent power differently, P/Q is not the PF ratio, and V/I defines impedance rather than the efficiency of power transfer.

Power factor describes how effectively electrical power is converted into useful work in an AC circuit. It is the cosine of the phase angle between voltage and current, reflecting the portion of the current that actually drives real power. When the angle is small, most of the current does useful work, so the power factor is near 1. When the angle is large, more current is needed for the same real power, increasing conductor losses (I^2R) and potentially utility penalties for poor PF.

This statement is correct because PF = cos φ, which directly links the real power portion to the total apparent power. The ideas that PF equals sin φ, equals P/Q, or equals V/I mix up different electrical quantities: sin φ relates to reactive vs. apparent power differently, P/Q is not the PF ratio, and V/I defines impedance rather than the efficiency of power transfer.