Using the model
Symbols, assumptions and limitations
Components are treated as ideal and the source is sinusoidal in steady state. Series branches add impedances; parallel branches add admittances. In RL or RC mode, omit the absent reactance or susceptance term from the displayed RLC formula. Parasitic resistance, inductor self-capacitance, capacitor ESR, tolerances, and frequency-dependent losses are not included.
Worked examples
See the method in practice
Series RLC at 50 Hz
For R = 100 Ω, L = 0.1 H, and C = 10 µF, XL ≈ 31.42 Ω and XC ≈ 318.31 Ω, so the circuit is predominantly capacitive.
Parallel RL
Parallel impedance is found by adding branch admittances, then taking the reciprocal; branch impedances must not be added directly.
Questions
Frequently asked
Why can impedance be complex?
The real part represents resistance; the imaginary part represents the net phase-shifting effect of inductance and capacitance.
What does a negative phase mean?
With the voltage-reference convention used here, a negative impedance angle indicates net capacitive behavior; a positive angle indicates net inductive behavior.
How is resonance identified?
For an RLC selection, the tool reports resonance when the impedance phase is within 0.5° of zero. This practical display threshold avoids requiring impossible exact slider equality.
Are component tolerances included?
No. Results use the selected nominal values and ideal-component equations.
Sources & review
Equations and examples are checked against the references below. Results are educational and should be independently verified for safety-critical work.
OpenStax University Physics — RLC series circuits with AC All About Circuits — Parallel R, L, and CWritten by the STEM Hub editorial team · Reviewed August 11, 2026 · Review methodology