LR circuits: An LR circuit contains an ideal 60-V battery, a 51-H inductor having no resistance, a 21-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. When the voltage across the resistor is equal to the voltage across the inductor, what is the current in the circuit?
A) 1.4 A
B) 0.57 A
C) 1.1 A
D) 0.86 A
E) 1.7 A

Question

Quizplus · Accepted Answer

When the voltage across the resistor is equal to the voltage across the inductor, the current in the circuit is equal to the voltage across the resistor divided by the resistance of the resistor. In this case, the voltage across the resistor is 30 V and the resistance of the resistor is 21 Ω, so the current in the circuit is 30 V / 21 Ω = 1.4 A.

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