Solving Kirchoff's Loop Rule: Is My Equation Correct?

In summary, the conversation is about a circuit and its corresponding equations. The person is questioning the correctness of their equations and asking for clarification on the signs used. They also mention a diagram on their website and seek advice from another person named berkeman. The conversation ends with the person confirming that their equations are correct and discussing the flow of currents in the circuit.
  • #1
willydavidjr
66
0
I have a diagram on my website and I also attached it to this message. My question is I am wondering if my equation for this loop rule is correct. I am trying to solve it but I am having a problem about the signs I am getting..

This is my equation for this loop:


[tex]I_2=I_1+I_3[/tex]

[tex]6V-2I_3-2I_2=0[/tex]

[tex]1V-2I_3-I_1=0[/tex]

Do you think the above equations are correct?I used the equations but I get different signs that doesn't match the circuit on the diagram...

This is the site of the circuit: www.geocities.com/willydavidjr/loop.html
 

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  • #2
Last equation is +I1. Look at the voltage *increase* through R1 in that direction due to I1.
 
  • #3
I see. Do you think berkeman the second equation should be 6V - 2I3 + 2I2=0? What do you think?
 
  • #4
I don't think that the third equation should be +I1. Because we will get negative answer for I3 and I1. Meaning they have opposite direction and it shouldn't be!
 
  • #5
willydavidjr said:
I see. Do you think berkeman the second equation should be 6V - 2I3 + 2I2=0? What do you think?

The second equation is fine as you wrote it (why do you think the sign is wrong ?). Just amend the third equation as berkeman suggested.

When taking a loop across a resistance, if going with the labelled flow of current, use the minus sign. If going against the labelled flow of current, use the plus sign.
 
  • #6
Berkeman what I get for this three equation just as I amended the 3rd equation are I1= 1 amp, I2= 1 amp and I3= 1 amp. Am I correct? I expected to get a negative value for I1 but I didn't get it. All have positive values. Do you think all flow of currents are correct?
 
  • #7
How can they all equal 1A when your first equation says I2=I1+I3 ?

When you get the answers, just go back and put them on the original drawing, and see if all the voltages and currents add up.
 
  • #8
No I mean 2A for I2. Sorry my fault.
 
  • #9
willydavidjr said:
No I mean 2A for I2. Sorry my fault.

I replied to your PM. The answer is correct.
 

1. What is Kirchoff's Loop Rule?

Kirchoff's Loop Rule, also known as Kirchoff's second law, states that the algebraic sum of the potential differences in any closed loop of a circuit must be zero. This means that the sum of the voltage drops and voltage rises in a loop must equal zero.

2. How do I use Kirchoff's Loop Rule to solve a circuit?

To use Kirchoff's Loop Rule, you need to first identify all the loops in the circuit. Then, write equations for each loop by assigning a direction (clockwise or counterclockwise) and sign (+ or -) for each voltage drop and rise in the loop. Finally, solve the system of equations to find the unknown values.

3. How do I know if my equation for Kirchoff's Loop Rule is correct?

To check if your equation for Kirchoff's Loop Rule is correct, you can use a simple test: add all the voltage drops and rises in the loop and see if the sum is equal to zero. If it is, then your equation is correct. Additionally, you can also double-check by solving the equation and comparing the result to the known values in the circuit.

4. Can I apply Kirchoff's Loop Rule to any circuit?

Yes, Kirchoff's Loop Rule can be applied to any circuit, as long as it is a closed loop. This means that the starting and ending points of the loop must be the same, and there can be no open branches in the loop.

5. Are there any common mistakes when using Kirchoff's Loop Rule to solve a circuit?

Yes, there are a few common mistakes that can occur when using Kirchoff's Loop Rule. These include forgetting to include a voltage source or resistor in the loop, using the wrong sign for a voltage rise or drop, and not setting up the equations properly. It is important to carefully identify all the loops and follow the direction and sign conventions to avoid these mistakes.

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