In an AC circuit, resonance frequency occurs when the inductive reactance (XL) equals the capacitive reactance (XC). This balance leads to maximum current flow. To derive the resonance frequency, use the formula: Resonance Frequency (f_r) = 1/{2 pi sqrt{LC}} where L is the inductance and C is the capacitance. This equation illustrates that at resonance, the product of inductance and capacitance determines the frequency at which the circuit becomes highly responsive. #PhysicsExamPrep #ACircuitBas