# Mistake in this node analysis work?

• influx
In summary: Therefore, the voltage drop will always be in the same direction as the current flow. The voltage rise will be in the opposite direction of the current flow.
influx

Is the working out for node V2 wrong? In particular, I am referring to the (V1-V2)/2 term in equation 2?

Also, is the voltage drop always in the same direction as the current or is the voltage rise always in the same direction as the current?

Thanks

Last edited:
Here is a good way to do nodal. have you ever heard of 'king of the hill' method?

You assume that your node is the point of highest potential.. that is, everything flows away from the node you're working on at that time. The signs will fall out correctly. Current sources are entered to the equations corresponding to their directions. Everything else is assumed leaving.

4Ix = V1/8 + (V1-V2)/2 (notice how everything was assumed to leave the node except current injections).

for node 2, you can do the same.

5-3Ix = V2/4 + (V2-V1)/2

Notice here in this equation we assumed V2 was at the higher potential. This is fine, as long as we assume it is the point of highest potential in all parts of the equation for that node.

I cannot solve the equations for you, but I sure hope this clarifies any confusion with Nodal analysis. ( I can say that the equations as I have written them are not quite where you want to start, you can entirely eliminate Ix from the equations).

Does it make sense? Any questions/corrections on what I have written are most welcome.

The trick is to leave the negative sign in front of the incoming currents, rather than expanding it out like you have done in the first term in equation 1. That way, you won't make common mistakes when identifying the correct direction of the current.
Also, if you move all your negative currents to the other side of the KCL equation, you should be able to see that the sum of all the incoming currents entering a node, equals the sum of all the outgoing currents leaving that node.

influx said:
Is the working out for node V2 wrong? In particular, I am referring to the (V1-V2)/2 term in equation 2?
I think it has been confirmed that that particular term doesn't belong in the equation. It's erroneous.

Also, is the voltage drop always in the same direction as the current or is the voltage rise always in the same direction as the current?
Current flows from higher potential towards lower potential.

for bringing this to my attention. After reviewing the node analysis work, I can confirm that there is a mistake in the equation for node V2. The (V1-V2)/2 term should actually be (V2-V1)/2. This is because in node analysis, we are looking for the voltage at each node relative to the reference node, and the voltage drop is always from higher potential to lower potential.

To answer your second question, the voltage drop and current direction are always in the same direction in a circuit. This is because the voltage drop is a measure of the potential difference between two points in a circuit, and the current flows from higher potential to lower potential. So, the voltage drop and current will always be in the same direction.

I will make the necessary corrections to the node analysis work and ensure that it is accurate. Thank you for bringing this to my attention and helping to improve the accuracy of our analysis. If you have any further questions or concerns, please do not hesitate to reach out.

## 1. What is node analysis in circuit analysis?

Node analysis is a method used in circuit analysis to find the voltage and current values at different points in a circuit by applying Kirchhoff's Current Law and Ohm's Law.

## 2. What is the most common mistake made in node analysis work?

The most common mistake in node analysis work is forgetting to include all the necessary nodes in the circuit or incorrectly labeling the nodes. This can lead to incorrect calculations and results.

## 3. How can I avoid making mistakes in node analysis work?

To avoid making mistakes in node analysis work, it is important to carefully label all the nodes in the circuit and double check that all nodes have been included in the analysis. Additionally, it is helpful to have another person review your work to catch any potential errors.

## 4. What should I do if I realize I made a mistake in my node analysis work?

If you realize you made a mistake in your node analysis work, it is important to go back and carefully review your calculations to identify the error. Once the mistake is identified, you can correct it and recalculate the values.

## 5. Are there any tools or software that can help with node analysis work?

Yes, there are various circuit analysis software programs that can assist with node analysis work. These programs can quickly and accurately calculate the values at different nodes in a circuit, reducing the likelihood of human error. It is still important to understand the principles behind node analysis and double check the results from the software.

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