# REAL QUICK HELP nodal analysis?

• asdf12312
In summary: I+4 instead of just I)In summary, the student is having trouble with their nodal equations. They are trying to find the current flowing between nodes 1 and 3. The equations for these nodes are (V1-4)/0.2, (V1-V2)/0.5, and (V1-V3)/0.5. The current is found using KVL, and it is -I flowing from V1 to V3.
asdf12312
REAL QUICK HELP nodal analysis??

n/a

## The Attempt at a Solution

i am having trouble with my nodal equations for nodes 1 and 3. and that's just for the current on the top of those nodes, where the 4V is at. For node 1 my current equation is (V1-4)/0.2 for the top. and for node 3 i got current is just 0A, because there's no resistor between it and the 4V source. but i know that can't be right...so i got at least one of those currents wrong. any quick thuoghts?Node 1:
(V1-2)/0.1 + (V1-4)/0.2 + (V1-V2)/0.5 = 0

Node 2:
(V2-V1)/0.5 + V2/0.1 + (V2-V3)/0.5 = 0

Node 3:
(V3-V2)/0.5 + (V3-3)/0.1 = 0

Keep in mind that the current you're looking for is due to the potential difference between nodes. So for your node 1 equation, the term for the upper path through the 4V supply should reference V3 too. The 4V supply is added to V3, so the potential difference becomes V1 - (V3 + 4).

One way to keep this straight is to use KVL along the path of interest. For the top branch you want to start at V1 and work your way over to V3. Assume the current is I flowing from V1 to V3, then

V1 - I*0.2 - 4 = V3

Rearrange:

I = (V1 - V3 - 4)/0.2

and that's your 'I' term for your node equation for that path.

Do the same for other branches that you find confusing. Note that the order of voltage sources and resistances along a given path doesn't matter.

Last edited:

thanks! was confusing for me at 1st but now i undrstand it. and the equation for the upper path from V3 to V1 would be (V3-V1)+4/0.2 (the polarity of the voltage source is switched. also the same as the negative value of current from V1 to V3.

## What is nodal analysis?

Nodal analysis is a method used in circuit analysis to determine the voltage and current at different nodes in a circuit. It is based on Kirchhoff's Current Law, which states that the sum of currents entering a node must equal the sum of currents leaving the node.

## How is nodal analysis different from other circuit analysis methods?

Nodal analysis is different from other circuit analysis methods, such as mesh analysis, because it focuses on the individual nodes in a circuit instead of the individual loops. It is also a more systematic approach, using equations to solve for unknown variables rather than relying on visual inspection.

## What are the advantages of using nodal analysis?

Nodal analysis has several advantages, including its ability to analyze complex circuits with multiple current sources and its efficiency in solving for multiple unknown variables. It also provides a clear understanding of the voltage and current at each node in a circuit, making it useful for design and troubleshooting.

## What are the limitations of nodal analysis?

Nodal analysis may become complicated and time-consuming for circuits with a large number of nodes. It also assumes that all currents and voltages are known or can be easily determined, which may not always be the case in real-world circuits.

## How can nodal analysis be applied in real-world situations?

Nodal analysis is commonly used in the design and analysis of electronic circuits, such as in the development of computer hardware, power supplies, and communication systems. It can also be used in other fields, such as in biology to model neural networks and in economics to analyze financial networks.

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