# RC circuit differential equations

1. Jun 30, 2010

### gjfelix2001

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

$$\frac{dV}{dt}=\frac{1}{C}(i(t)-\frac{V}{R})$$

and

$$I = \frac{dQ}{dt}=\frac{1}{R}(V-\frac{Q(t)}{C})$$

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. Jul 1, 2010

### n.karthick

Do you know how to use Laplace transform to solve differential questions?

3. Jul 1, 2010

### gjfelix2001

RC circuit: is this the right equation?

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

$$I(t) = \frac{dQ}{dt}=\frac{Q(t)}{CR}-\frac{V}{R}$$

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
4. Jul 3, 2010

### jasonRF

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