Red Seal Electrician Practice
AC theoryQuestion 980 of 1506

A series R-L-C circuit is on a 120 V supply. A technician measures 137 V across the capacitor. What explains this?

  1. The meter is faulty, because no part can exceed the supply voltage
  2. The capacitor is shorted and passes the full supply voltage
  3. The reactances cancel and the current rises
  4. The inductor is acting as a second source of power
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Correct answer: The reactances cancel and the current rises

The two reactances oppose, so the total impedance is low. The larger current makes a part voltage that can exceed the supply.

Source: Lessons in Electric Circuits II: AC (Kuphaldt), 5.2: Series R, L, and C

Practice ac theory

Questions last reviewed: 18 October 2026