Node Voltage Method in Circuit Analysis

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Discussion Overview

The discussion revolves around the application of the Node Voltage Method in circuit analysis, specifically focusing on the calculation of currents at a node involving resistors and a voltage source. Participants are exploring the reasoning behind certain voltage and current relationships in the circuit.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant expresses confusion about the calculation of current in a branch involving a 1 ohm resistor and a 4 ohm resistor, questioning the use of equivalent resistance in the context of node voltage.
  • Another participant clarifies that the current in the branch is calculated as (v0-45)/5, suggesting a conceptual approach of combining resistors to simplify the circuit analysis.
  • A participant challenges the idea of moving a resistor in relation to a battery, questioning how this affects the equivalent circuit.
  • Further clarification is provided that the position of the resistors does not affect the current flow, emphasizing that both resistors influence the total current from the battery.
  • One participant acknowledges the importance of understanding the voltage source in the analysis, indicating that this realization was crucial for their comprehension.

Areas of Agreement / Disagreement

Participants express differing views on the conceptual understanding of resistor placement and its impact on circuit analysis. There is no consensus on the clarity of the explanation regarding the movement of resistors and its implications for current calculation.

Contextual Notes

Participants are working with assumptions about voltage differences and equivalent resistance that may not be fully articulated. The discussion reflects varying levels of understanding regarding the Node Voltage Method and its application in this specific circuit scenario.

Who May Find This Useful

Individuals studying circuit analysis, particularly those interested in the Node Voltage Method and the relationships between voltage, current, and resistance in electrical circuits.

Noesis
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I really don't understand exactly how they got the term highlighted in yellow.

We want to get all values for all of the currents coming into or out of the node...so why does it have what appears to be the voltage across the 1 ohm resistor divided by the equivalent resistance of the 1 ohm and 4 ohm?

Wouldn't the current out that branch be vo/5 anyway?

Someone please help.

Thank you guys.
 

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No, the current in that branch is (v0-45)/5 as they have written. Conceptually you can move the 1 ohm resistor down to the position of the 4 ohm, making it 5 ohms instead. That might make it clear to you that the voltage across the 5 ohm resistor is v0-45.
 
Thanks for the reply Marcus!

Why? That doesn't make much sense really.

How can just moving a resistor 'over' a battery produce an equivalent circuit?
 
It does not matter the position of the 4 ohm resistor; whether its on the wire that connects to the negative end of the battery or the positive. What matters here is that the same amount of current will flow though both. In other words, both of these resistors will control the current flow. Leave the circuit as is and just trace the total current coming out from one terminal of the battery, you will find that the same amount flows through both resistors.

Wouldn't the current out that branch be vo/5 anyway?
But we have 45V source on one end and vo on the other; neither of which are 0V. Voltage is the difference of electrical potential between two points.
 
Last edited:
Thank you very much Ranger.

I couldn't have understood it without your reply. Realizing what to do with the 45V source was crucial.
 

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