Question
What is the magnitude of the circulating current within the components of a parallel LC circuit at resonance?
Answer Options
- A) It is at a minimum
- B) It is at a maximum
- C) It equals 1 divided by the quantity 2 times pi, times the square root of (inductance L multiplied by capacitance C)
- D) It equals 2 times pi, times the square root of (inductance L multiplied by capacitance C)
Correct Answer: B
Explanation
In a parallel LC circuit, the current flowing into the external circuit (from the power source) is minimal at resonance because the large reactive currents flowing in the capacitor and the inductor cancel each other out in the external line. However, inside the parallel tank circuit itself, the energy is oscillating back and forth between the inductor and the capacitor.
This continuous exchange of energy results in the circulating current within the components of a parallel LC circuit being at a maximum at resonance. The magnitude of this current is approximately equal to the Q of the circuit multiplied by the current drawn from the source. Because this circulating current is so high, components in high-Q parallel resonant circuits must be rated to handle this large current flow, even if the external current drawn is very small.
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