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In an LCR series circuit with R = 20 Ω, L = 50 mH, and C = 40 μF at 60 Hz, what is the phase angle between voltage and current?

Correct answer: B. 67.8°

  • A. 15.2°
  • B. 67.8°
  • C. 36.9°
  • D. 45.0°

Explanation

ω = 2π × 60 ≈ 376.8 rad/s. XL = ωL = 376.8 × 0.05 ≈ 18.84 Ω.Xc = 1 / (ωC) . = 1 / (376.8 × 40 × 10⁻⁶) ≈ 66.35 Ω. Net reactanceX = Xc - XL = 66.35 - 18.84 ≈ 47.51 Ω. Phase angle φ = tan⁻¹(X /R) = tan⁻¹(47.51 / 20) ≈ tan⁻¹(2.375) ≈ 67.8 ° (current lagsvoltag

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About Alternating Current

Alternating current varies periodically, so phase relationships become essential when current passes through a resistor, capacitor or inductor. The chapter distinguishes resistance from capacitive and inductive reactance, explains phase lead and lag, and connects changing electric and magnetic fields with the production and properties of electromagnetic waves.

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