 #1
 2
 0
In the following circuit R1 = 12.9 Ohms, R2 = 3 Ohms, V = 39 Volts, and C = 10.1 microFarads. If one waits 2 time constants after the battery has been connected (charge in capacitor is zero before the battery is connected), what is the voltage across R1 in volts? Hint: first find the charge in capacitor after this amount of time, and then find the voltage across the capacitor. Use a loop rule to find voltage across the equivalent resistor and use this to find the current in the circuit at this time.
I attached a picture.
I tried solving it by first using Q = CV to find Qmax. My Qmax was 393.9 micro coulombs. I then multiplied this number by 0.63 because 1e^(2/2) is 0.63. This number was 248 micro coul. After finding this number i plugged it back into the Q = CV equation to solve for the new V and I got 24.57. I thought I could subtract the V's and get the answer, but its not working out. Can someone help me out?
I attached a picture.
I tried solving it by first using Q = CV to find Qmax. My Qmax was 393.9 micro coulombs. I then multiplied this number by 0.63 because 1e^(2/2) is 0.63. This number was 248 micro coul. After finding this number i plugged it back into the Q = CV equation to solve for the new V and I got 24.57. I thought I could subtract the V's and get the answer, but its not working out. Can someone help me out?
Attachments

8.7 KB Views: 368