In an inductive circuit, which quantity leads the other?

In an inductive circuit, which quantity leads the other?

• A. Current leads voltage
• B. Voltage lags current
• C. Voltage leads current
• D. Voltage and current are in phase

Answer: (C)

In an inductive circuit, the inductor resists changes in current, so the voltage across it is tied to how quickly the current is changing. Mathematically, v = L di/dt, meaning the voltage is proportional to the rate of change of current. For a sinusoidal excitation, this makes the current lag the voltage by 90 degrees. In phasor form, V = jωL I, which shows the voltage leading the current by 90 degrees. Therefore, the quantity that leads is the voltage. The current lags, and they are not in phase.

In an inductive circuit, the inductor resists changes in current, so the voltage across it is tied to how quickly the current is changing. Mathematically, v = L di/dt, meaning the voltage is proportional to the rate of change of current. For a sinusoidal excitation, this makes the current lag the voltage by 90 degrees. In phasor form, V = jωL I, which shows the voltage leading the current by 90 degrees. Therefore, the quantity that leads is the voltage. The current lags, and they are not in phase.