A 4.0-MΩ resistor is connected in series with a 0.50-μF capacitor. The capacitor is initially uncharged. The RC combination is charged by a 9.0-V battery. What is the change in voltage between t = RC and t = 3RC?
A)15 V
B)11 V
C)7.6 V
D)5.7 V
E)2.9 V

Question

Quizplus · Accepted Answer

The voltage across a charging capacitor in an RC circuit is given by V(t) = V0(1 - e^(-t/RC)). At t = RC, V(RC) = 9(1 - e^(-1)) ≈ 5.7 V. At t = 3RC, V(3RC) = 9(1 - e^(-3)) ≈ 8.1 V. The change in voltage is 8.1 V - 5.7 V = 2.4 V, which is closest to 2.9 V.

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