Direction and magnitude of the current

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Homework Help Overview

The discussion revolves around determining the direction and magnitude of the current in a circuit involving resistors and a voltage source, specifically focusing on a horizontal wire between points a and e. The subject area includes circuit analysis and application of Kirchhoff's laws.

Discussion Character

  • Exploratory, Problem interpretation, Assumption checking

Approaches and Questions Raised

  • Participants discuss applying Kirchhoff's loop rule to multiple loops in the circuit. There is consideration of simplifying the circuit by combining resistors in parallel, and questions arise regarding how to calculate the equivalent resistance and the values of currents I1 and I2.

Discussion Status

The discussion is active with participants exploring different methods for circuit analysis. Some guidance has been offered regarding the use of parallel resistor formulas, but there remains uncertainty about the representation of variables in the equations and how to proceed with finding the equivalent resistance.

Contextual Notes

Participants are working under the constraints of the problem statement, which includes specific resistor values and a voltage source. There is an ongoing discussion about the definitions and roles of variables in their equations, indicating potential confusion in the setup.

zooropa
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Homework Statement


Taking R = 1.00 kΩ and ε = 250 V in the figure, determine the direction and magnitude of the current in the horizontal wire between a and e.
http://img5.imageshack.us/img5/7250/img001nkm.th.jpg


Homework Equations


Kirchhoff´s law


The Attempt at a Solution


I must try to apply Kirchhoff´s loop rule to both rules?
 
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Yes, all three loops. Or perhaps you could combine the 4R and 3R in parallel to get a simpler circuit with only two loops. Once you know I1 and I2, it should be easy to find I in the original circuit.
 
I think it will be done with 4R and 3R in parallel. But how can i have the value of the new R?
 
Last edited:
If i have the new value of R i could find I1 and I2, like this:
(xR)I1+(yR)I2=250
and
(xR)I1+(yR)I2=500

I think it will be the solution, but the problem is that i can't find the new value of x and y if i combine the 4R and 3R in parallel to get a simpler circuit with only two loops.
Any help? Thanks
 
The 4R and 3R (4000 and 3000 ohms) are in parallel. You must use the formula for the resistance of two resistors in parallel.

I don't understand what your x and y represent.
It seems to me the current through the combined resistors would be I1 + I2, so the equations will each have one more term than you have shown.
 

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