# RC complete response help

Discussion in 'Math' started by jcb19, Mar 31, 2013.

1. ### jcb19 Thread Starter New Member

Feb 20, 2013
14
0
Hi. Could someone check whether my answers for the following question are correct as I havent been supplied any answers to check and have an exam soon. Thanks

A 12V DC source is connected in series to a 4ohm resistor and 1000μF capacitor. At t=0, the switch is closed. Calculate;

1. Initial (t=0) current in the circuit
2. Initial resistor voltage
3. Final capacitor voltage
4. time constant of the circuit
5. current in the circuit at t=6ms
6. final energy stored in the capacitor.

1. initial current = E/R = 12/4 = 3A
2. Initial resistor voltage = 12V
3. Final Capacitor voltage = 12V (Because resistor voltage falls to ≈0)
4. ζ = CR = 1000x10^-6 x 4 = 4ms
5. current at 6ms = Io x e^-t/CR = 3 x e^-6/4 = 0.67A
6. Final Energy = 1/2CV^2 = 0.5 x 0.001 x 12^2 = 0.072J
Thanks.

2. ### WBahn Moderator

Mar 31, 2012
22,985
6,882
At a quick glance it looks like you are okay.

But you need to get in the habit of tracking your units through your work.