Kirchhoff's Laws: Homework Solutions Check

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The discussion centers on verifying homework solutions related to Kirchhoff's Laws, specifically focusing on current and voltage equations. Participants express concerns about potential mistakes in the signs of currents I1 and I2, noting that their calculations yield both currents as positive. There is a debate about the necessity of the positive sign accompanying current arrows, with some finding it redundant and cluttering the diagram. The conversation highlights the importance of clarity in representing currents and the mathematical implications of sign conventions. Overall, the thread emphasizes the need for careful attention to detail in applying Kirchhoff's Laws.
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Homework Statement



2s1n338.png


Homework Equations



\sum I_{in} = \sum I_{out}
\sum \epsilon = \sum pd

The Attempt at a Solution



Can anyone identify any mistakes in these? Probably signs

I = I_1 + I_2
12=4I_1 +3I
5=4I_1 - 2I_2
12-5=2I_2+3I
 
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What let's you think there are any mistakes ?
 
BvU said:
What let's you think there are any mistakes ?
The answers have I1 and I2 with opposite signs. I get them both as positive.
 
I make all currents positive for the directions shown.

I'm not sure what is achieved by that + sign accompanying each current arrow? It seems superfluous if it duplicates the function of the arrowhead, and just clutters the diagram.
 
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NascentOxygen said:
I make all currents positive for the directions shown.

I'm not sure what is achieved by that + sign accompanying each current arrow? It seems superfluous if it duplicates the function of the arrowhead, and just clutters the diagram.
Well that's good news. And, yeah, I guess it's just intended to help with the maths side of things.
 

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