Circuit Problem with Kirchoff's rules (ugh)

  • Thread starter Thread starter Color_of_Cyan
  • Start date Start date
  • Tags Tags
    Circuit Rules
AI Thread Summary
The discussion revolves around solving a circuit problem using Kirchhoff's rules, specifically focusing on determining the current in each branch. Participants emphasize the importance of simplifying resistors in series and the need to draw and label currents in each branch. There is confusion regarding the application of Kirchhoff's voltage and current laws, particularly in creating the necessary equations. Suggestions include marking the voltage at a reference node and writing Kirchhoff's voltage law (KVL) equations based on that. Overall, the thread highlights the challenges faced in applying these fundamental circuit analysis techniques.
Color_of_Cyan
Messages
386
Reaction score
0

Homework Statement

Determine the current in each branch of the circuit shown (here:)
[PLAIN]http://img811.imageshack.us/img811/5084/physicschapter2817.jpg

Homework Equations


Kirchoff's rules, I think is (and I'm probably looking at it wrong):

summation of ΔV around closed loops is 0,

summation of current at any junction is 0(Current) = ΔV / (Resistance), etc

Resistors connected in series = (R1 + R2 +...), etc

The Attempt at a Solution


The red spike lines are resistors.

I am just totally stunned here. This problem got to me to the point of me having to put it here and to draw it in MS paint, and sorry if it looks like an ugly drawing...Anyway the only thing I can do right now is to just simplify the resistors first. Two of em are connected in series so the resistors on the right are simplified to 4 ohms and the ones on the middle line become 6 ohms.

It seems very hard to apply Kirchoff's rules at all and I am not sure how to do apply Kirchoff's rules here. Also I am not sure on what the problem means by "each branch of the circuit. And with the batteries it's even more confusing.
 
Last edited by a moderator:
Physics news on Phys.org
Two pairs of resistors can be simplified (which ones?) To start this problem, you need to draw currents in each branch of the circuit and label them i1, i2 etc. Assume a direction; if your assumption is incorrect, when you put in the numbers the currents will be negative. For this circuit you will need two sum of voltages equations and one sum of currents equation.

For future reference, you can draw resistors as skinny rectangles and if you label each as as a number followed by Ω (or "Ohms"), everyone will know them for what they are.
 
kuruman said:
Two pairs of resistors can be simplified (which ones?) To start this problem, you need to draw currents in each branch of the circuit and label them i1, i2 etc. Assume a direction; if your assumption is incorrect, when you put in the numbers the currents will be negative. For this circuit you will need two sum of voltages equations and one sum of currents equation.

For future reference, you can draw resistors as skinny rectangles and if you label each as as a number followed by Ω (or "Ohms"), everyone will know them for what they are.
I think I may want to know how to make summation of voltages equations and that's probably where I'm having trouble.

I'll get other help from this in the meantime and check back in.
 
Here's your circuit redrawn with the simplifications that you've already described.

attachment.php?attachmentid=37998&stc=1&d=1313373523.gif


There are three branches. I've also labelled two of the nodes as "a" and "b", and we can assume that node "b" represents a common reference point (designated here by the circuit "ground" symbol at node b).

Suppose for the sake of argument that you happened to know the voltage (with respect to node b) at node a. Call it Va. Can you mark the diagram with currents for each branch and then write KVL equations for those currents for each of them using Va?
 

Attachments

  • Fig1.gif
    Fig1.gif
    1.5 KB · Views: 585
Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
Thread 'Correct statement about a reservoir with an outlet pipe'
The answer to this question is statements (ii) and (iv) are correct. (i) This is FALSE because the speed of water in the tap is greater than speed at the water surface (ii) I don't even understand this statement. What does the "seal" part have to do with water flowing out? Won't the water still flow out through the tap until the tank is empty whether the reservoir is sealed or not? (iii) In my opinion, this statement would be correct. Increasing the gravitational potential energy of the...
Thread 'A bead-mass oscillatory system problem'
I can't figure out how to find the velocity of the particle at 37 degrees. Basically the bead moves with velocity towards right let's call it v1. The particle moves with some velocity v2. In frame of the bead, the particle is performing circular motion. So v of particle wrt bead would be perpendicular to the string. But how would I find the velocity of particle in ground frame? I tried using vectors to figure it out and the angle is coming out to be extremely long. One equation is by work...
Back
Top