Solve a Circuit Problem: Node-Voltage Method

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Discussion Overview

The discussion revolves around a circuit problem involving the node-voltage method, specifically addressing the role of various voltage and current sources in the circuit configuration. Participants are exploring the implications of these sources on the overall circuit analysis and the discrepancies between their calculations and a provided answer manual.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • The original poster describes their approach using the node-voltage method and expresses confusion regarding the omission of a 150 Volt source in the answer manual.
  • Some participants propose that the configuration of the voltage and current sources in series effectively behaves as a current source, which may justify ignoring the voltage source in certain calculations.
  • Others challenge this view, suggesting that the voltage source should contribute to the current through the bottom resistor, indicating that it cannot simply be ignored.
  • There is mention of using MATLAB for solving the equations derived from the node-voltage method, highlighting a reliance on computational tools for circuit analysis.

Areas of Agreement / Disagreement

Participants exhibit disagreement regarding the treatment of the 150 Volt source in the circuit analysis. Some believe it can be ignored due to the series configuration with the current source, while others argue that it should be included in the calculations.

Contextual Notes

Participants have not reached a consensus on the correct approach to the problem, and there are unresolved questions regarding the representation of the voltage and current sources in the node-voltage equations.

Novean
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Homework Statement



Here's a link to a picture of the problem:
http://i.imgur.com/zMAiR.png

V(delta) is above the 7 Ohm resistor, and V(x) is described by the positive Node between the 7 Ohm resistor and the 5 Amp Source, and the negative Node between the 9 ohm resistor and 150 Volt Source.

i(omega) runs down the 4 Ohm source on the left.

The top dependent voltage source is 3*V(x)
The left dependent voltage source is 5*i(omega)
The right dependent voltage source is 13*v(delta)

Homework Equations



I advise to use the node-voltage method to solve this. Plus, it will help me understand it since that and the Current-mesh are the tools our professor expects us to know for the coming exam.

The Attempt at a Solution



I have spent far too many hours and countless papers and methods trying to solve this problem in a way that gave me the answer that the book has. I've begun to think that the book may be wrong in regards to their answer?

Anyway, I'll detail my usual procedure:

Using the node-voltage method:

I chose to ground the node in the top between the 1 Ohm and 2 Ohm resistors. Since a wire connect that node to the one under it, I concluded that both of those nodes are grounded. I pretty much erased that wire and connected both nodes into one.

I then created node-voltage equations, and use a program called MATLAB to solve matrices that I created out of the linear equations (As my professor has told us to do for every problem).

The answer in the answer manual says that the Power absorbed is 23.68 W.
They show a procedure to doing it, but they always skip the 150 Volt source in their equations. It's as if it doesn't exist. Why is this?

If someone could either do it and get the right answer, or tell me why they chose to omit the 150 Voltage source in their calculations, that'd help me greatly. Also, you could just tell me a different method to doing the problem and I'll give it a go.

What really has me confused is the usage of the Voltage and Current source on the bottom wire. I don't know how to represent those in a node-voltage equation correctly.

Thank you if you can help me in anyway.
 
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We have voltage source and current source in series. This configuration gives constant current at any voltage so it is actually current source.
 
szynkasz said:
We have voltage source and current source in series. This configuration gives constant current at any voltage so it is actually current source.

So what you're saying is that they are right in that they ignore the 150 Voltage source?
Cause the way I'm thinking is that the voltage source would also create a current through the bottom resistor, such that the current in the bottom can be represented as a sum of the Current source and Voltage source through the resistor.
 
The current source produces 100 mA current regardless of what is connected to it.
 

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