Engineering Nodal analysis question -- circuit analysis

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The discussion revolves around using nodal analysis to find the current in a given circuit. The user attempts to derive equations for two nodes but struggles to match their result with the expected answer from the textbook. Suggestions are made to verify the capacitor value and to reformulate the node equations to sum all currents leaving the node, which may simplify the analysis. The user is encouraged to reassess their equations for potential errors. Overall, the focus is on correcting the approach to achieve the correct current calculation.
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Homework Statement


We have the circuit in the figure.I have to find the current i using nodal analysis
PPsWAsW.jpg


Homework Equations


1/6 F =-3j
1/2 F= -j
1/2 H= j

The Attempt at a Solution



So we have the equations
Node V1 : [(7-V1)/(4-3j) ]=[ V1/3 ]+ [(V1-V)/-j]
Node V : [(V1-V)/-j] =(V )+ (V/j)
In the V node we multiply by j each side so we have -(V1-V)=jV+V so -V1=jV
I place this in the first node so we have
In the first node we have [(7+jV)(4+3j)]/[(4-3j)(4+3j)] = -jV/3 + [(-jV-V)/-j]
We have 1.12 +0.84j-0.16jV-0.12V=-0.33JV+V-jV
Here I find V =0.1+0.85j
Now to find i I think I need to divide this by 1/2 H so by j
Problem is ,the result in my book is i=0.75 cos2t which I don't get here so where is my mistake?
 
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Elaia06 said:

Homework Statement


We have the circuit in the figure.I have to find the current i using nodal analysis
PPsWAsW.jpg


Homework Equations


1/6 F =-3j
1/2 F= -j
1/2 H= j

The Attempt at a Solution



So we have the equations
Node V1 : [(7-V1)/(4-3j) ]=[ V1/3 ]+ [(V1-V)/-j]
Node V : [(V1-V)/-j] =(V )+ (V/j)
In the V node we multiply by j each side so we have -(V1-V)=jV+V so -V1=jV
I place this in the first node so we have
In the first node we have [(7+jV)(4+3j)]/[(4-3j)(4+3j)] = -jV/3 + [(-jV-V)/-j]
We have 1.12 +0.84j-0.16jV-0.12V=-0.33JV+V-jV
Here I find V =0.1+0.85j
Now to find i I think I need to divide this by 1/2 H so by j
Problem is ,the result in my book is i=0.75 cos2t which I don't get here so where is my mistake?

First, the value of the left capacitor looks to be 1/6 Farad, not 1/3 Farad, right? Does that change your first equation?

Second, I prefer to write the node equations as the sum of all currents leaving the node = 0. That way I don't have to worry about signs of currents.

Could you see if you want to change the first equation, and maybe re-write the equations in the form that I suggested? That will make it a lot easier to check your work. Thanks.
 

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