Confusion with Kirchhoff's Law in Circuit Diagram

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The discussion revolves around applying Kirchhoff's first law to a circuit diagram, with multiple-choice equations provided. Participants express confusion about the circuit's drawing and the direction of current I3. It is clarified that the assumed direction of current does not affect the validity of Kirchhoff's law, as negative values can indicate direction. Users are encouraged to identify the sum of currents entering and leaving the nodes to formulate the correct equation. The conversation emphasizes understanding the principles of current flow in circuit analysis.
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Homework Statement


I have this circuit diagram (see attached), and the question is: Which of the following equations is Kirchhoff's first rule as applied to the above circuit?
With the answers:
I1 + I2 + I3 = 0
I1 - I2 + I3 = 0
I1 + I2 - I3 = 0
I1 - I2 - I3 = 0
(it's multiple choice)
The


Homework Equations


sum of Iin = sum of I out


The Attempt at a Solution


I can't even begin. I understand Kirchoff's laws pretty well, but it just appears to me that the circuit is drawn wrong.

What am I doing wrong?
 

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It seems that your attached diagram isn't attached :smile:
 
gneill said:
It seems that your attached diagram isn't attached :smile:

Now it is :smile:
 
Apply the equation that you posted. What is the sum of currents going in? What is the sum of currents coming out? Look at your drawing.
 
I see that the diagram has the currents labeled on each branch. Why don't you add some more such arrows nearer the nodes where the currents come together or diverge? Note that the current in any given series connected branch is always the same current!
 
kuruman said:
Apply the equation that you posted. What is the sum of currents going in? What is the sum of currents coming out? Look at your drawing.

I see part of it, but shouldn't the current in I3 flow the other direction?
 
jforce93 said:
I see part of it, but shouldn't the current in I3 flow the other direction?

Whether the actual current flows in the other direction or not does not matter; it simply means that when the equations are solved and calculations are completed with the assumed direction, it will yield a negative value for that current.

Take the assumed directions as given and write the equation from them.
 
gneill said:
Whether the actual current flows in the other direction or not does not matter; it simply means that when the equations are solved and calculations are completed with the assumed direction, it will yield a negative value for that current.

Take the assumed directions as given and write the equation from them.

okay, thanks
 

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