Electrical mathQuestion 964 of 1506

A 30 ohm resistor is in series with a capacitor that has 40 ohms of reactance. What is the total impedance?

  1. 70 ohms
  2. 10 ohms
  3. 50 ohms
  4. 35 ohms
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Correct answer: 50 ohms

Resistance and reactance are 90 degrees apart, so Z = √(30² + 40²) = √2500 = 50 ohms.

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

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Questions last reviewed: 18 October 2026