KVL Node Voltage: Positive vs Negative Assumption in Homework Solution

In summary, the conversation discusses the difference in approach between the book and the professor regarding the polarity of a voltage source in a circuit. This difference ultimately affects the potential at node a, and the given answers may be incorrect depending on the polarity of the voltage source.
  • #1
cpatel23
16
0

Homework Statement



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Homework Equations



ƩCurrent(in) = ƩCurrent(out)

The Attempt at a Solution


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----In situations like that, my book takes the node to be a positive voltage when the voltage source is connected like above. For some reason my professor takes it to be negative, is this why my answer is different?


(sorry for the big pictures)
 
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  • #2
The potential at node a with respect to the reference node depends entirely upon the polarity of the 4V source. The picture is a bit fuzzy around that source, but it appears that the "+/-" indicator shows "+" at the top. That would make node a +4V. It would also make the indicated answers incorrect.

If the 4V source polarity were reversed, then node a would be at potential -4V with respect to ground, and the given answers would then look good.
 

Related to KVL Node Voltage: Positive vs Negative Assumption in Homework Solution

What is KVL (Kirchhoff's Voltage Law) in circuit analysis?

KVL is a fundamental law in circuit analysis that states that the sum of all voltage drops in a closed loop in a circuit must equal the sum of all voltage sources in that same loop.

What is a node in circuit analysis?

A node in circuit analysis refers to a point in a circuit where two or more components are connected together. It is represented by a dot in circuit diagrams and is used to apply KVL and KCL (Kirchhoff's Current Law) equations.

How do you apply KVL to a simple circuit with only one voltage source?

In a simple circuit with only one voltage source, you can apply KVL by writing a single equation that equates the voltage source to the sum of all voltage drops across the components in the circuit. This equation can then be solved to find the unknown voltage values at each node.

What is the node voltage method?

The node voltage method is a systematic approach to solving circuits using KVL. It involves assigning a reference node, usually the ground, and writing KVL equations for each node in the circuit with respect to the reference node. These equations can then be solved simultaneously to find the unknown node voltages.

Why is the node voltage method useful?

The node voltage method is useful because it allows for the analysis of complex circuits with multiple voltage sources and components. It also provides a systematic and organized approach to solving circuits, making it easier to understand and troubleshoot any issues that may arise.

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