• $summary_{type}$: concept
• $word_{count}$: 170

Inductive reactance $X_L$ = omega*L increases linearly with frequency — an inductor passes DC freely but increasingly opposes higher frequencies. Capacitive reactance $X_C$ = $\frac{1}{omega*C}$ 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$\frac{(X_L - X_C}{R}$) determines whether voltage leads (inductive) or current leads (capacitive). Power factor cos(phi) = $\frac{R}{Z}$. 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.