Difficulty: Easy
Correct Answer: Correct
Explanation:
Introduction / Context:Series resonance is a cornerstone concept in AC circuit theory and filter/tank design. It occurs when the inductive reactance equals the capacitive reactance in magnitude (X_L = X_C), causing reactances to cancel so the impedance is purely resistive and minimal.
Given Data / Assumptions:
Concept / Approach:Impedance of a series RLC is Z = R + j(X_L − X_C). At resonance, X_L = X_C → Z = R (minimum magnitude). Ohm’s law shows I = V/Z is largest when |Z| is smallest (for fixed V), hence current peaks at resonance. Large reactive voltages may appear across L and C individually, but the net reactive effect in the loop is zero at resonance.
Step-by-Step Solution:
Write Z(f) = √(R^2 + (X_L − X_C)^2).At f = f_0, X_L = X_C → |Z| = R (minimum possible for that circuit).Thus I(f_0) = V/R is the maximum attainable loop current for that applied V.Verification / Alternative check:Plot I versus frequency (a resonance curve). The peak occurs at f_0. Bandwidth relates to quality factor Q = X_L/R at resonance.
Why Other Options Are Wrong:
“Incorrect”: contradicts Z minimization at resonance.“Only if R = 0”: even with finite R, current is maximal at resonance for that V.“Parallel resonance”: refers to a different topology where current dips in the feed branch.“XL = 2XC”: not the resonance condition.Common Pitfalls:Confusing series and parallel resonance characteristics; focusing on large VL or VC and missing that total impedance is minimized, not maximized.
Final Answer:Correct
Discussion & Comments