Question

The variation of impedance Z of a series LCR circuit with frequency of the source is shown in the figure. Which of the following statement(s) is/are true?

• A. The impedance Z is inductive in the portion AC
• B. The impedance Z is capacitive in the portion BC.
• C. The impedance Z is inductive in the portion BC.
• D. The impedance Z is capacitive in the portion AB

Hint:

In an LCR circuit, the impedance is inductive at low frequencies, capacitive at high frequencies, and at resonance, the impedance is purely resistive.

Answer 1

The Correct Option is C, D

1. Step 1: The impedance of an LCR circuit depends on the frequency of the source. As the frequency changes, the relative contributions of the inductive, capacitive, and resistive components change.
2. Step 2: In a series LCR circuit:
   • At low frequencies, the impedance is dominated by the inductive reactance, making the circuit inductive in that region.
   • As the frequency increases, the impedance shifts to capacitive behavior where the capacitive reactance dominates.
3. Step 3: From the given figure, in the portion BC, the impedance shows capacitive behavior because the impedance decreases with increasing frequency, indicating capacitive reactance.

Conclusion: In the portion BC, the circuit's impedance is dominated by capacitive reactance due to its decreasing nature with frequency.