Please Help Me with Physics?

Question

I would appreciate any helpful input on this physics problem. I am really confused on this one. Thanks for any help :)

Consider a series RC circuit for which R = 9.0 MΩ, C = 8.0 µF, and E = 27 V. Find the charge on the capacitor 15 seconds after the switch is closed (The answer is in µC).

Answer 1

This is actually an exponential "decay" problem, since the voltage approaches an asymptote (27 V). The time constant TC = R*C = 72 sec. The capacitor voltage Ec = 27 * (1-e^(-t/TC)) or 5.078 V. The charge is Ec*C = 0.00004062 C = 40.62 uC.

Answer 2

i dont have an answer for the question but i havent herd from you in awhile so i thought id say hello .