🔌 RLC Circuit Resonance
AC CircuitsCommon questions
What is resonance in an RLC circuit?
Resonance occurs when inductive reactance equals capacitive reactance (XL = XC). At this frequency, impedance is minimum (Z = R), current is maximum, and the circuit behaves purely resistively.
How does the quality factor affect resonance?
Higher Q means a sharper, narrower resonance peak. Q = (1/R)√(L/C). High-Q circuits are more selective — useful in radio tuning and filters.
What happens to impedance at resonance frequency?
Impedance drops to its minimum value equal to resistance R. Below resonance the circuit is capacitive, above resonance it is inductive.
Why is RLC resonance important for JEE?
RLC circuits appear in JEE Main and Advanced every year. Questions test resonance frequency calculation, Q-factor, bandwidth, and phase relationships.
How to calculate resonance frequency?
f₀ = 1/(2π√LC). This is independent of resistance. Higher L or C lowers the resonance frequency. This formula must be memorised for JEE.