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Nodal analysis help

  • #1

Homework Statement


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
 

Answers and Replies

  • #2
NascentOxygen
Staff Emeritus
Science Advisor
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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.
 
  • #3
gneill
Mentor
20,781
2,759
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.
 
  • #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
 
  • #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
 
  • #6
gneill
Mentor
20,781
2,759
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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