Define electrical power factor and its unitless nature.

Define electrical power factor and its unitless nature.

• A. The cosine of the phase angle between voltage and current; dimensionless, ranges from -1 to 1.
• B. The ratio of reactive power to real power.
• C. The voltage divided by current.
• D. The angle between voltage and current expressed in degrees.

Answer: (A)

Power factor is the cosine of the phase angle between voltage and current in an AC system. This angle tells how much the current lags or leads the voltage. When the angle is zero, the current and voltage are in sync and the power factor is at its maximum value of one, meaning all the power is real and usable. As the angle grows, the cosine decreases, signaling that some power is reactive and not doing useful work in each cycle. The unitless nature comes from it being a ratio (real power divided by apparent power) and from the cosine of an angle, so no units appear. Since cos(phi) ranges from -1 to 1, you can also get negative values for leading or lagging conditions beyond 90 degrees. In practice, we usually discuss the magnitude from 0 to 1, with the sign indicating whether the current leads or lags. The other ideas—reactive power to real power ratio, voltage divided by current, or the angle itself in degrees—do not define power factor.

Power factor is the cosine of the phase angle between voltage and current in an AC system. This angle tells how much the current lags or leads the voltage. When the angle is zero, the current and voltage are in sync and the power factor is at its maximum value of one, meaning all the power is real and usable. As the angle grows, the cosine decreases, signaling that some power is reactive and not doing useful work in each cycle. The unitless nature comes from it being a ratio (real power divided by apparent power) and from the cosine of an angle, so no units appear. Since cos(phi) ranges from -1 to 1, you can also get negative values for leading or lagging conditions beyond 90 degrees. In practice, we usually discuss the magnitude from 0 to 1, with the sign indicating whether the current leads or lags. The other ideas—reactive power to real power ratio, voltage divided by current, or the angle itself in degrees—do not define power factor.