A 45-mH inductor is connected in series with a 60-Ω resistor through a 15-V dc power supply and a switch. If the switch is closed at t = 0 s, what is the current after 7.0 ms?
A) 250 mA
B) 650 mA
C) 550 mA
D) 280 mA
E) 850 mA

Question

Quizplus · Accepted Answer

The current in an RL circuit after time t is given by I(t) = (V/R)(1 - e^(-Rt/L)). Substituting V = 15 V, R = 60 Ω, L = 0.045 H, and t = 0.007 s, we find I(7 ms) ≈ 0.25 A or 250 mA.

A 45-MH Inductor Is Connected in Series with a 60-Ω