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 AC

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: An LCR circuit's impedance varies with the source frequency. The contributions of inductance, capacitance, and resistance change as frequency changes.
2. Step 2: For a series LCR circuit:
   • At low frequencies, inductive reactance dominates, making the circuit inductive.
   • As frequency rises, the circuit's behavior becomes capacitive due to dominant capacitive reactance.
3. Step 3: In the BC portion of the figure, the circuit acts capacitively. This is because impedance decreases with increasing frequency, a characteristic of capacitive reactance.

Conclusion: Capacitive reactance dominates the circuit's impedance in the BC portion, as evidenced by its decrease with frequency.