What is impedance in an RLC circuit?
Impedance is the total opposition a series RLC circuit presents to alternating current, combining the resistor’s constant resistance with the frequency-dependent reactance of the inductor and capacitor. Unlike plain resistance, impedance also has a phase component describing how voltage and current shift relative to each other.
The formulas used
Inductive reactance is Xl = 2πfL and capacitive reactance is Xc = 1 / (2πfC). For a series circuit these combine as the net reactance X = Xl – Xc, and the total impedance magnitude is |Z| = √(R² + X²). The phase angle between voltage and current is θ = atan(X / R).
Enter the resistance, inductance, capacitance, and the frequency of interest to see how the circuit behaves at that specific frequency — inductive (positive phase), capacitive (negative phase), or purely resistive at resonance where Xl equals Xc. This tool is for general electronics education and reference.