AC theoryQuestion 1483 of 1506

A series circuit has a resistance of 100 Ω and a capacitive reactance of 40 Ω. What is the impedance?

  1. 140 Ω
  2. 63.2 Ω
  3. 70.0 Ω
  4. 108 Ω
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Correct answer: 108 Ω

Z = √(R² + X²) = √(100² + 40²) = 108 Ω. Resistance and reactance are 90° apart, so they do not add directly.

Source: Computed, 4.3: Series Resistor-Capacitor Circuits

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Questions last reviewed: 18 October 2026