Confusion with Kirchhoff's Law in Circuit Diagram

In summary: So the answer is that current in I3 goes in the opposite direction of the current in I1, I2, and I3. Kirchhoff's first rule is not applied to the circuit.
  • #1
jforce93
26
0

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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  • #2
It seems that your attached diagram isn't attached :smile:
 
  • #3
gneill said:
It seems that your attached diagram isn't attached :smile:

Now it is :smile:
 
  • #4
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.
 
  • #5
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!
 
  • #6
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?
 
  • #7
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.
 
  • #8
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
 

What is Kirchoff's law confusion?

Kirchoff's law confusion refers to the common misunderstanding or confusion surrounding Kirchoff's laws of circuit analysis. These laws, named after German physicist Gustav Kirchoff, are fundamental principles used to analyze and solve electrical circuits.

What are Kirchoff's laws?

Kirchoff's laws consist of two principles: Kirchoff's current law (KCL) and Kirchoff's voltage law (KVL). KCL states that the algebraic sum of currents entering and exiting a node (or junction) in a circuit must equal zero. KVL states that the algebraic sum of voltages around a closed loop in a circuit must equal zero.

Why are Kirchoff's laws important?

Kirchoff's laws are important because they provide a systematic approach for analyzing and solving complex electrical circuits. They allow scientists and engineers to predict the behavior of circuits and design them accordingly. These laws are also used to troubleshoot circuit problems and ensure that circuits are operating properly.

What are some common misconceptions about Kirchoff's laws?

One common misconception is that KCL and KVL only apply to DC circuits. In reality, these laws apply to both DC and AC circuits. Another misconception is that KCL and KVL are independent of each other. In fact, they are complementary principles that work together to provide a comprehensive analysis of a circuit.

How can I remember Kirchoff's laws?

A common way to remember Kirchoff's laws is to use the mnemonic "KCL: Keep Calm and Leave" and "KVL: Keep Voltage Levels". Another helpful tip is to practice solving circuit problems using these laws, as repetition can aid in memory retention. Additionally, understanding the underlying principles and concepts behind the laws can make them easier to remember and apply.

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