Which term best describes theta in the AC power formula?

Which term best describes theta in the AC power formula?

• A. Frequency of the electrical supply
• B. Voltage magnitude
• C. The phase angle between voltage and current
• D. Current magnitude

Answer: (C)

In AC power, theta represents the phase angle between the voltage and current. Voltage and current are sinusoidal and can be out of sync because reactive elements (like inductors and capacitors) cause them to lead or lag each other. That angle tells you how far apart the waveforms are in time. It’s the angle that determines the power factor, since real power is P = VI cos theta. When theta is zero, voltage and current are perfectly in phase and you get the full product VI as real power. If theta is positive or negative, part of that power is reactive, described by Q = VI sin theta. The other options describe frequency or the magnitudes of voltage or current, which are not theta.

In AC power, theta represents the phase angle between the voltage and current. Voltage and current are sinusoidal and can be out of sync because reactive elements (like inductors and capacitors) cause them to lead or lag each other. That angle tells you how far apart the waveforms are in time. It’s the angle that determines the power factor, since real power is P = VI cos theta. When theta is zero, voltage and current are perfectly in phase and you get the full product VI as real power. If theta is positive or negative, part of that power is reactive, described by Q = VI sin theta. The other options describe frequency or the magnitudes of voltage or current, which are not theta.