LR circuits: 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^(-Rt/L), where V_0 is the initial voltage (60 V), R is the resistance (24 Ω), and L is the inductance (42 H). Solving 24 = 60 * e^(-24t/42) gives t ≈ 1.6 s.

LR Circuits: an LR Circuit Contains an Ideal 60-V Battery