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.
    Answers

    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
    17,719
    4,788
    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.
     
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