• summary_type: concept
• word_count: 170

Inductive reactance X_L = omegaL increases linearly with frequency — an inductor passes DC freely but increasingly opposes higher frequencies. Capacitive reactance X_C = 1/(omegaC) decreases with frequency — a capacitor blocks DC but freely passes high frequencies. Both have units of ohms but dissipate no power. In a series LCR circuit, impedance Z = sqrt(R^2 + (X_L - X_C)^2). The impedance triangle has R as the base, (X_L - X_C) as the perpendicular, and Z as the hypotenuse. The phase angle phi = arctan((X_L - X_C)/R) determines whether voltage leads (inductive) or current leads (capacitive). Power factor cos(phi) = R/Z. The phasor diagram is the visual representation: V_R along the current direction, V_L perpendicular leading, V_C perpendicular lagging. The resultant V is the vector sum. This triangle is the single most powerful tool for solving AC circuit problems.