Circuit Problem with Kirchoff's rules (ugh)

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Homework Help Overview

The problem involves analyzing a circuit using Kirchhoff's rules to determine the current in each branch. Participants are discussing the setup and simplification of resistors within the circuit.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to simplify the circuit by combining resistors in series but expresses confusion about applying Kirchhoff's rules and the meaning of "each branch." Other participants suggest drawing currents in each branch and labeling them, while also questioning which resistors can be simplified.

Discussion Status

Participants are actively exploring different interpretations of the circuit and discussing the necessary steps to apply Kirchhoff's rules. Some guidance has been offered regarding labeling currents and simplifying the circuit, but there is no explicit consensus on the approach yet.

Contextual Notes

There is mention of confusion regarding the circuit's layout and the implications of the battery connections. The original poster also indicates difficulty in understanding how to formulate the necessary equations for voltage and current.

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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.
 
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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?
 

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