試題詳解

18. Consider the circuit in the figure, in which V = 30 V, R₁ = 10 Ω, R₂ = 15 Ω, R₃ = 30 Ω, and L = 20 mH. The switch is initially open. If the switch is closed for a long time and reopened, what is the voltage across R₂ when the switch is reopened?

 
(A) 7.5 V
(B) 15 V
(C) 22.5 V
(D) 30 V
(E) 45 V