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RC circuit differential equations

  1. Jun 30, 2010 #1
    Hi everyone...

    I need to solve the differential equations of a RC circuit given a voltage and a current pulse. I have to get this responses:

    http://i.imagehost.org/view/0340/Respuesta1 [Broken]

    I'm using matlab, with runge kutta. I've been solving the equations separately changing the initial conditions and the value of current and voltage, but i want to know if there is a way to get the response solving the differential equations only once??

    By the way, the differential equations i'm trying to solve are

    [tex]\frac{dV}{dt}=\frac{1}{C}(i(t)-\frac{V}{R})[/tex]

    and

    [tex]I = \frac{dQ}{dt}=\frac{1}{R}(V-\frac{Q(t)}{C}) [/tex]

    How should i solve this equations in order to get the responses showed in the pictures???
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Jul 1, 2010 #2
    Do you know how to use Laplace transform to solve differential questions?
     
  4. Jul 1, 2010 #3
    RC circuit: is this the right equation?

    Hi everybody, i'm trying to solve the equation:

    [tex]I(t) = \frac{dQ}{dt}=\frac{Q(t)}{CR}-\frac{V}{R}[/tex]

    in order to get this graph (V changes to simulate the pulse)

    [PLAIN]http://i.imagehost.org/0340/Respuesta1.jpg [Broken]

    I'm not getting this response, and i've checked my program (runge kutta) with a current pulse and works ok... So the only way i'm not getting what i want is that the differential equation i'm solving is wrong. Please, can you tell me the correct equation?? Thanks!!
     
    Last edited by a moderator: May 4, 2017
  5. Jul 3, 2010 #4

    jasonRF

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    Science Advisor
    Gold Member

    Re: RC circuit: is this the right equation?

    If you drew the circuit you cared about I think we could help. Trying to "reverse engineer" what you are really interested in is a lot to ask!

    jason

    jason
     
    Last edited by a moderator: May 4, 2017
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