Lesson 10.8: Alternating Current (AC) Circuits - Summary

Key Concepts: Alternating Current (AC) Circuits

Alternating Current

  • AC current and voltage vary sinusoidally: V = V₀ sin(ωt), I = I₀ sin(ωt).
  • RMS values: V_rms = V₀/√2, I_rms = I₀/√2. These are the equivalent DC values for power calculations.

AC Circuit Components

  • Resistor: V and I are in phase. P = I²R.
  • Capacitor: Current leads voltage by 90°. Reactance: X_C = 1/(ωC).
  • Inductor: Voltage leads current by 90°. Reactance: X_L = ωL.

Impedance

  • Z = √(R² + (X_L − X_C)²) — total opposition to AC.
  • Resonance: When X_L = X_C (ω = 1/√(LC)), impedance is minimum (Z = R) and current is maximum.

Transformers: V₂/V₁ = N₂/N₁. Step-up (N₂ > N₁) increases voltage; step-down decreases it.

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