Question on Kirchoff's Laws

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In summary: Keep up the good work!In summary, the conversation is about a problem with Kirchoff's Laws and calculations for a circuit with a battery, two parallel resistors, and two mesh loops. The equations and values are discussed, and it is determined that the results obtained from Kirchoff's Laws do not match Ohm's Law. After further clarification, the issue is resolved and the conversation ends on a positive note.
  • #1
ahben86
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I was hoping someone could help out, I am working out a problem with Kirchoff's Laws and cannot seem to get the math to work out properly, at least I think the math is not working properly.
I was hoping to run it by someone here.

Homework Statement



The circuit is as follows:
A battery of 24 V on one end connected to two parallel resistors with values of 5 Ω and 7 Ω.
Mesh one will be the loop between the battery and the 5 Ω resistor, which has a current of I1.
Mesh two will be the loop between the 5 Ω resistor and the 7 Ω resistor, which has current of I2.

Homework Equations


The equations I set up are as follows:
0 = -24 + 5*(I1 - I2)
0 = 7*I2 + 5*(I2 - I1)




The Attempt at a Solution


After calculating the values I obtained these numbers:
I1 = 8.229 A
I2 = 3.429 A

I tried verifying these answers by using V = I*R
Finding Req to be 2.917 Ω.
Therefore I = V/R and I = 8.228 A and since the current from I1 is the same value it seems that the values obtained from Kirchoff's Laws do not match the Ohm's Law current.

I am uncertain if I am not realizing a concept but this does not make sense to me.

Any help is appreciated.
Thank you,
A.B.
 
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  • #2
I think your work is all correct. V =IR finds the current through the resistors as 4.8 and 3.42 representing I1 - I2 and I2, so I2 = 3.42,
I1 - I2 = 4.8
I1 = I2 + 4.8
I1 = 3.42 + 4.8 = 8.23
 
  • #3
thank you for your help Delphi, sorry I posted in the wrong area.
I think I understand now,

A. B.
 
  • #4
Most welcome! This is the correct area for your question.
 
  • #5




Hello A.B.,

Thank you for reaching out for help with your problem involving Kirchoff's Laws. It seems like you have set up the equations correctly, but there may be a mistake in your calculations. I would suggest double checking your math to ensure accuracy. Additionally, it may be helpful to draw out the circuit and label all the components and currents to visualize the problem better.

In terms of verifying your answers using Ohm's Law, it is important to note that the currents calculated using Kirchoff's Laws are the total currents in each loop, whereas the current calculated using Ohm's Law is the current through a single resistor. This is why the values may not match exactly. However, the total current through the entire circuit should still be equal to the total current calculated using Ohm's Law.

I hope this helps. If you are still having trouble, don't hesitate to reach out for further assistance. Good luck with your problem!

Best,
 

1. What are Kirchoff's Laws?

Kirchoff's Laws are a set of fundamental principles that govern the behavior of electrical circuits. These laws were developed by German physicist Gustav Kirchoff in the mid-19th century and are used to analyze and solve complex electrical circuits.

2. What is Kirchoff's Current Law (KCL)?

Kirchoff's Current Law states that the total current entering a junction in a circuit must be equal to the total current leaving the junction. In other words, the algebraic sum of all currents at a junction must equal zero.

3. What is Kirchoff's Voltage Law (KVL)?

Kirchoff's Voltage Law states that the algebraic sum of all voltages around a closed loop in a circuit must be equal to zero. This means that the total voltage drop across all elements in a closed loop must equal the total voltage applied to that loop.

4. How are Kirchoff's Laws used in circuit analysis?

Kirchoff's Laws are used to analyze and solve complex electrical circuits by creating a system of equations based on the conservation of current and energy. These equations can then be solved to determine the values of currents and voltages at different points in the circuit.

5. What are some practical applications of Kirchoff's Laws?

Kirchoff's Laws are used in a wide range of practical applications, including designing and troubleshooting electronic circuits, calculating power distribution in electrical grids, and analyzing data in neuroscience research. They are also used in various engineering fields, such as aerospace, telecommunications, and power systems.

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