Calculating of currents in a circuit

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AI Thread Summary
The discussion focuses on applying Kirchhoff's laws to analyze a circuit with two contours involving three batteries and a resistor. The first contour equation relates the voltages and currents in a counterclockwise direction, while the second contour incorporates a different path through the circuit. Participants confirm that the equations appear correct and suggest testing them with a simple case, such as identical batteries in parallel, to verify consistency. They emphasize the importance of using different loops to cross-check results, ensuring that the final answers align regardless of the chosen path. Proper application of Kirchhoff's laws is crucial for accurate calculations in circuit analysis.
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Homework Statement
Three e. sources are connected as shown in the diagram.
What is the current flowing through the conductor and the sources when
it is known that E1=1.3 V, E2=1.5 V, E3=2V, r1=r2=r3=0.2 Ω, (##r##)
R=0.55 Ω.
Relevant Equations
Kirchhoff's 1st and 2nd laws;
##V=IR##
I am marking the current flowing through the conductor the same as currect flowing through the E3. (I3)
I am thinking of using Kirchhoff's laws in two contours. 1st contour would be the small one (E1 and E2) counter clock wise. 2nd contour would go through E3,E2,R (wouldn't go through E1).

For 1st contour (CCW):
##E_{1}-E_{2}=r(I_{1}-I_{2})##
2nd contour (CCW):
##E_{3}+E_{2}=I_{3}(r+R)+I_{2}r##
And Kirchhoff's 1st law for left node:
##I_{3}=I_{1}+I_{2}##

Now, that I have system of equations, I can calculate for everyone of them. (only if I applied Kirchhoff's laws correctly, of which I am not sure)
My question is: Did I apply the laws correctly and are these equations OK?
 

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It looks OK. You can also try them for some simple case. Like what happens if the two batteries in parallel are identical? Do you get the right result from your equations for this particular case?
 
It helps to have a diagram with the currents and their (assumed) directions marked.

You can check your work by solving with different loops. I would have chosen:
cell-1 to R to cell-3 back to cell-1 and
cell-2 to R to cell-3 back to cell-2.

You should, of course, get the same final answer whichever loops you use.
 
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