What is the inductance of a series RL circuit in which R = 1.0 K$\Omega$if the current increases to one-third of its final value in 30 $\mu$s?
A)74 mH
B)99 mH
C)49 mH
D)62 mH
E)none of the above

Question

Quizplus · Accepted Answer

The time constant τ for an RL circuit is given by τ = L/R. The current reaches one-third of its final value at t = τ * ln(3). Given R = 1000 Ω and t = 30 μs, solve for L: L = R * t / ln(3) = 1000 * 30e-6 / ln(3) ≈ 74 mH.

What Is the Inductance of a Series RL Circuit in Which