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Homework Help: Need help simplifying equation to find the laplace transform of it

  1. Sep 16, 2005 #1
    there are two loops in an electrical circuit. ive got two equations and two unknowns.
    here are the equations

    v(t) = I1*R1 + 1/c*int(I1*dt) - 1/c*int(I2*dt) - first loop
    0 = LdI2/dt + R2*I2 - 1/c*int(I1*dt) + 1/c*int(I2*dt) - second loop

    the capacitor is in the branch between the two loops.

    Im drawing a blank on this. I need to simplify into one equation so I can find the laplace transform of the one equation.
    the goal is to find the step response of the system using matlab.
  2. jcsd
  3. Sep 16, 2005 #2

    Tom Mattson

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    Staff Emeritus
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    Gold Member

    You'll want to differentiate both equations first, to get rid of those god awful integrals.

    There's nothing wrong with taking the Laplace transform first and then simplifying.
  4. Sep 17, 2005 #3
    can i get a confirmation that i set up those differential equations properly? im having some trouble with this still. if i differentiate, than i get derivative of the input. im trying to find the output voltage which is across the R2 resistor.
  5. Sep 19, 2005 #4
    im still having trouble with this problem. ive tried multiple methods including differentiation and solving for a variable and plugging it into the first equation but im still where i started the other day. im trying to find an eqation that relates the output voltage across R2 to the input. im confident my beginning equations are correct, but i dont know where to go from there.
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