Question
What happens when inductive and capacitive reactance are equal in a series LC circuit?
Answer Options
- A) Resonance causes impedance to be very high
- B) Impedance is equal to the geometric mean of the inductance and capacitance
- C) Resonance causes impedance to be very low
- D) Impedance is equal to the arithmetic mean of the inductance and capacitance
Correct Answer: C
Explanation
In a series circuit containing an inductor (L) and a capacitor (C), the circuit is in resonance when the inductive reactance (X_L) precisely equals the capacitive reactance (X_C). Since inductive reactance and capacitive reactance are opposite in phase (+jX and -jX respectively), they cancel each other out completely when equal.
The total impedance (Z) of a series LC circuit is Z = R + j(X_L - X_C). At resonance, since X_L = X_C, the reactive component goes to zero, leaving only the circuit’s inherent resistance (R). Because this resistance is typically very small, resonance causes impedance to be very low. This allows maximum current flow through the series circuit at the resonant frequency.
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