Question

Find the effective impedance in the circuit if the source is: a) DC source and b) High frequency AC source

• A. For DC, \( Z = R_2 + R_3 \) and for AC, \( Z = R_1 + R_3 \)
• B. For DC, \( Z = R_1 \) and for AC, \( Z = R_2 + R_3 \)
• C. For DC, \( Z = \infty \) and for AC, \( Z = 0 \)
• D. For DC, \( Z = 0 \) and for AC, \( Z = \infty \)

Hint:

For DC, capacitors behave like open circuits, and inductors behave like short circuits. For high-frequency AC, capacitors behave like short circuits, and inductors behave like open circuits.

Answer 1

The Correct Option is B

For DC, the inductors act as short circuits (because their reactance is zero) and the capacitors act as open circuits (because their reactance is infinite). Therefore, the impedance for a DC source is simply \( Z = R_1 \). For high-frequency AC, the inductors act as high-impedance elements, and the capacitors act as low-impedance elements. Therefore, the impedance for a high-frequency AC source is \( Z = R_2 + R_3 \), as the inductors contribute effectively to the impedance while the capacitors' reactance approaches zero.