Consider the capacitor-resistor-diode circuit shown in the figure. The capacitor is 20 μF and the resistor is 100 Ω. Of the two identical diodes, the forward-biased diode has resistance 10 Ω, while the other diode is reverse biased. What is the time constant of the circuit?

Question

G1 Physics · Accepted Answer

Only the forward-biased diode conducts. Its resistance of 10 Ω is in series with the 100 Ω resistor. Therefore the effective resistance seen by the capacitor is R(eq) = 100+10 = 110 Ω. The time constant is τ = R(eq)C = 110×20×10⁻⁶ = 2200×10⁻⁶ s = 2.2×10⁻³ s. Correct option: A.