Need help simplifying equation to find the laplace transform of it

In summary, the conversation is about finding the step response of an electrical circuit using two equations and two unknowns, with a capacitor located between the two loops. The goal is to simplify the equations into one so that the Laplace transform can be taken. There is a struggle in finding the correct equation to relate the output voltage across R2 to the input.
  • #1
formulajoe
177
0
there are two loops in an electrical circuit. I've 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.
 
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  • #2
You'll want to differentiate both equations first, to get rid of those god awful integrals.

I need to simplify into one equation so I can find the laplace transform of the one equation.

There's nothing wrong with taking the Laplace transform first and then simplifying.
 
  • #3
can i get a confirmation that i set up those differential equations properly? I am having some trouble with this still. if i differentiate, than i get derivative of the input. I am trying to find the output voltage which is across the R2 resistor.
 
  • #4
im still having trouble with this problem. I've tried multiple methods including differentiation and solving for a variable and plugging it into the first equation but I am still where i started the other day. I am trying to find an equation that relates the output voltage across R2 to the input. I am confident my beginning equations are correct, but i don't know where to go from there.
 

1. What is the Laplace transform and why is it used?

The Laplace transform is a mathematical tool used to solve differential equations and analyze systems in engineering and physics. It converts a function of time into a function of complex frequency, making it easier to solve complex problems involving time-varying systems.

2. How do I simplify an equation to find the Laplace transform?

To simplify an equation for the Laplace transform, you can use various operations such as linearity, time shifting, differentiation, and integration properties. These properties allow you to transform the original equation into a form that is easier to solve using tables, graphs, or other mathematical techniques.

3. Can I use the Laplace transform on any equation?

No, the Laplace transform can only be applied to functions that satisfy certain conditions, such as being piecewise continuous, having exponential order, and being of bounded variation. If these conditions are not met, the Laplace transform may not converge or may give incorrect results.

4. Are there any common mistakes to avoid when using the Laplace transform?

Yes, some common mistakes when using the Laplace transform include forgetting to include initial conditions, incorrectly applying the time-shifting property, or not using the correct transform for the given function. It is important to carefully apply the properties and check your work for accuracy.

5. How can I check if I have correctly simplified an equation for the Laplace transform?

You can check your work by applying the inverse Laplace transform to the transformed equation and comparing it to the original equation. If the results match, then you have correctly simplified the equation. Additionally, you can use tables or software tools to verify your results.

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