Question

The figure shows an experimental plot for discharging of a capacitor in an R-C circuit. The time constant τ of this circuit lies between

(a) 0 and 50 sec
(b) 50 sec and 100 sec
(c) 100 sec and 150 sec
(d) 150 sec and 200 sec

Answer 1

(c) : During discharging of a capacitor
V = V₀e^–t/τ
where t is the time constant of RC circuit.
At t = τ, V = V₀/e=0.37V₀
From the graph, t = 0, V₀ = 25V
∴ V = 0.37 × 25V = 9.25V
This voltage occurs at time lies between 100sec and 500sec. Hence, time constant τ of this circuit lies between 100sec and 150sec.