Red Seal Electrician Practice
AC theoryQuestion 956 of 1506

A source feeds a resistor only. How do the voltage and current waveforms compare?

  1. Current leads voltage by 90 degrees
  2. They are in phase
  3. Current lags voltage by 90 degrees
  4. They are 180 degrees apart
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Correct answer: They are in phase

In a resistor the current is directly proportional to the voltage at every instant, so the waves rise and fall together.

Source: Lessons in Electric Circuits II: AC (Kuphaldt), 4.1: AC Resistor Circuits (Capacitive)

Practice ac theory

Questions last reviewed: 18 October 2026