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Nodal analysis help

  1. Oct 17, 2015 #1
    1. The problem statement, all variables and given/known data
    Using nodal analisis we need obtain the differential equation

    2. The attempt at a solution


    For I1 and take the point under C as reference, but i am stuck on it
    PA170007.JPG
     
  2. jcsd
  3. Oct 18, 2015 #2

    NascentOxygen

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    Staff: Mentor

    Hi Jair Gutierrez. :welcome:

    The next step here is to add those 3 currents, and equate the result to 0; this gives you your second order DE.

    You don't have the right expression for I1, the current in an inductor.
     
  4. Oct 18, 2015 #3

    gneill

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    Staff: Mentor

    Is Va entirely arbitrary or does it have some particular form? I'm assuming it's a source rather than the desired output from some initial value conditions of the circuit... the problem statement is rather vague.
     
  5. Oct 18, 2015 #4
    Hi thanks for your anwers, yes I1 is an inductor,
    I1=integral of (Va-V1)/L, but in all this equations where i use the resistor R, i think R is part of I1, but i dont know how write the equation in this case.

    Here is the original exercise, 5.15 PA150002.JPG
     
  6. Oct 18, 2015 #5
    In my node i have 3 currents, I1, I2, I3, i think R is part of I1, but how I involve R1 to form part of the equation for I1

    PA180009.JPG
     
  7. Oct 18, 2015 #6

    gneill

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    Staff: Mentor

    The potential at the left side of L1 is not Va since, as you say the resistor R is between it and the reference node. There will be a potential drop across R due to ##I_1##. So the potential across L1 is going to be something like: ##(-I_1 R + V_a - V_1)##.
     
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