KVL Node Voltage: Positive vs Negative Assumption in Homework Solution

AI Thread Summary
The discussion centers on the confusion regarding the voltage assumption at a node in a KVL (Kirchhoff's Voltage Law) problem. The participant notes a discrepancy between their textbook, which assumes a positive voltage at the node due to the polarity of a 4V source, and their professor's assumption of a negative voltage. This difference in assumptions leads to varying answers in their homework. The polarity of the voltage source is crucial, as reversing it would change the node's potential from +4V to -4V, aligning the answers with the professor's expectations. Understanding the correct polarity is essential for accurate KVL analysis.
cpatel23
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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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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.
 

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