A resistor, an uncharged capacitor, a dc voltage source, and an open switch are all connected in series. The switch is closed at time t = 0 s. Which one of the following is a correct statement about
This circuit?
A) The charge on the capacitor after one time constant is 1/e of its maximum value.
B) The charge on the capacitor after four time constants is about 98% of the maximum value.
C) The voltage on this capacitor after one time constant is 100% of its maximum value.
D) The voltage on the capacitor after one time constant is 1/e of the maximum value.
E) The charge on the capacitor after one time constant is 50% of its maximum value.

Question

Quizplus · Accepted Answer

After one time constant, the charge on a capacitor in an RC circuit is about 63% of its maximum value, not 1/e or 50%. After four time constants, the charge is indeed about 98% of its maximum value, making option B correct.

A Resistor, an Uncharged Capacitor, a Dc Voltage Source, and an Open