Red Seal Electrician Practice
AC theoryQuestion 967 of 1506

In a series R-C circuit, how do the voltage across the capacitor and the current through it compare?

  1. The voltage is in phase with the current
  2. The voltage leads the current by 90 degrees
  3. The voltage lags the current by 90 degrees
  4. The voltage lags the current by 45 degrees
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Correct answer: The voltage lags the current by 90 degrees

Even inside a mixed circuit, an individual capacitor keeps its 90-degree voltage-current relationship.

Source: Lessons in Electric Circuits II: AC (Kuphaldt), 4.3: Series Resistor-Capacitor Circuits

Practice ac theory

Questions last reviewed: 18 October 2026