An a.c. series circuit has a resistance of 4 Ω and an inductive reactance of 3 Ω. What is its impedance?
Correct answer D. 5 Ω
Explanation
Resistance and reactance are 90° out of phase, so they add as vectors: Z = √(R² + X²) = √(16 + 9) = 5 Ω.
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