An LR circuit contains an ideal 60-V battery,a 42-H inductor having no resistance,a 24-Ω resistor,and a switch S,all in series.Initially,the switch is open and has been open for a very long time.At time t = 0 s,the switch is suddenly closed.How long after closing the switch will the potential difference across the inductor be 24 V?
A) 1.6 s
B) 1.4 s
C) 1.8 s
D) 1.9 s
E) 2.1 s

Question

Quizplus · Accepted Answer

The potential difference across the inductor is given by V_L = V_0 * e^(-t/τ), where τ = L/R. Here, V_0 = 60 V, V_L = 24 V, L = 42 H, and R = 24 Ω. Solving for t when V_L = 24 V gives t ≈ 1.6 s.

An LR Circuit Contains an Ideal 60-V Battery,a 42-H Inductor