# Determine current and voltage using Node Voltage method

• Daeol
In summary, the conversation is about determining UR3 and IR3 using the Node-Voltage method in a circuit. The first step is to determine the currents at nodes A, B, and C. The equations for each node are rewritten to form a system of equations to solve for UA, UB, and UC. The person is hesitant about some of the current notations and wants to make sure they are correct before moving on to solving the system of equations. There is also a discussion about the notations on the voltage source and the importance of defining the direction of all currents.
Daeol
[Mod note: Post moved to new thread, so template not included]

Hello there again!

I started working on the second problem but I think I am doing it wrong so I thought I would post the first step and do this one step at a time to see where the mistake was.

So the task is to determine UR3 and IR3 using the Node-Voltage method. Also I hope it is not an issue that I am posting this here, I thought it would be better than creating a new thread.

This is the circuit:

So first thing I did is that I determined the currents that flow through the nodes A B and C.

A: I1 + IR2 - IR1 - IR3 = 0
B: IR3 + I2 - IR5 = 0
C: IR5 + IR4 - I2 = 0

Now to rewrite those so that I can get a system of 3 equations where I need to solve for UA, UB and UC.

A: I1 + (U+UB-UA)/R2 - UA/R1 - (UB-UA)/R3 = 0
B: (UB-UA)/R3 + I2 - (UB-UC)/R5 = 0
C: (UB-UC)/R5 + UC/R4 - I2 = 0

So that would be it for the start I guess. Let me know what do you guys think, if I got the currents going in and out right and all.

I am especially hesitant about IR2 = (U+UB-UA)/R2 IR3 = (UB-UA)/R3 and IR5 = (UB-UC)/R5.

I need to make sure I do this step correctly before I move on to solving the system of equations.

The notations on the voltage source are confusing. There's both an arrow and a "+ -" indication, and they are showing opposite polarities. Which one are we to believe?

if you're going to do node analysis, you need to define the direction of all currents, always do 'current in', or always do current out.
that being said your equations look correct.

## 1. How is the Node Voltage method used to determine current and voltage?

The Node Voltage method is a technique used in circuit analysis to determine unknown currents and voltages in a circuit. It involves identifying and labeling the different nodes (connection points) in a circuit and using Kirchhoff's Current Law (KCL) and Ohm's Law to write and solve equations for the unknown variables.

## 2. What are the advantages of using the Node Voltage method?

The Node Voltage method is advantageous because it allows for a systematic and organized approach to solving complex circuits. It also reduces the number of equations needed to solve a circuit compared to other methods, making it more efficient and less prone to errors.

## 3. How do you identify the nodes in a circuit for the Node Voltage method?

To identify the nodes in a circuit, look for the points where three or more elements, such as resistors, are connected. These points will have the same voltage and can be labeled as a single node. It is important to label the nodes consistently and correctly to ensure accurate calculations.

## 4. Can the Node Voltage method be used for any type of circuit?

Yes, the Node Voltage method can be used for any type of circuit, including circuits with multiple voltage sources, dependent sources, and both series and parallel elements. However, it is most effective for circuits with several interconnected nodes.

## 5. Are there any limitations to using the Node Voltage method?

The Node Voltage method can become more complex and time-consuming for circuits with a large number of nodes. In these cases, other methods such as the Mesh Current method may be more suitable. It also assumes that the circuit is linear and does not account for non-linear elements such as diodes and transistors.

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