- #1
QuietQuasar
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I am having trouble with circuit diagram involving multiple currents. We were taught the method of using junction/loop rules and systems of equations (or matrices) to find the current or voltage in a given spot. I think I understand the basic concept but am setting up my equations incorrectly.
Find the current in the 10.0[tex]\Omega[/tex] resistor in the drawing (V1 = 15.0 V and R1 = 27.0[tex]\Omega[/tex])
http://dl.dropbox.com/u/307214/20_82alt.gif
Kirchoff's rules...I don't think any actual equations?
First I decided to pick a common start point for the problem as the lower right corner.
Then I labeled the currents in the circuit: I[tex]_{A}[/tex] as going to the right in the left branch, I[tex]_{B}[/tex] going to the right in the right branch, and I[tex]_{C}[/tex] going up across the middle.
I then setup 2 of my equations by going in a loop from my start point and adding or subtracting the voltages, so:
+15 + 10 - 27I[tex]_{A} [/tex] - 5I[tex]_{B}[/tex] =0 for going around the left branch and
15 + 10 - 10I[tex]_{C} [/tex] - 5I[tex]_{B}[/tex] =0 for going up the middle.
I then determined (perhaps incorrectly) that I[tex]_{A}[/tex]+I[tex]_{B}[/tex] =I[tex]_{C}[/tex]
From here I setup matrices on my calculator as such:
Matrix [A]
-27 -5 0
0 -5 -10
1 1 -1
and
Matrix
-25
-25
0
I then did [A][tex]^{-1}[/tex]* for the results:
.7042
1.1972
1.9014
None of these answers are correct :/
Any and all help is greatly appreciated!
-QQ
Homework Statement
Find the current in the 10.0[tex]\Omega[/tex] resistor in the drawing (V1 = 15.0 V and R1 = 27.0[tex]\Omega[/tex])
http://dl.dropbox.com/u/307214/20_82alt.gif
Homework Equations
Kirchoff's rules...I don't think any actual equations?
The Attempt at a Solution
First I decided to pick a common start point for the problem as the lower right corner.
Then I labeled the currents in the circuit: I[tex]_{A}[/tex] as going to the right in the left branch, I[tex]_{B}[/tex] going to the right in the right branch, and I[tex]_{C}[/tex] going up across the middle.
I then setup 2 of my equations by going in a loop from my start point and adding or subtracting the voltages, so:
+15 + 10 - 27I[tex]_{A} [/tex] - 5I[tex]_{B}[/tex] =0 for going around the left branch and
15 + 10 - 10I[tex]_{C} [/tex] - 5I[tex]_{B}[/tex] =0 for going up the middle.
I then determined (perhaps incorrectly) that I[tex]_{A}[/tex]+I[tex]_{B}[/tex] =I[tex]_{C}[/tex]
From here I setup matrices on my calculator as such:
Matrix [A]
-27 -5 0
0 -5 -10
1 1 -1
and
Matrix
-25
-25
0
I then did [A][tex]^{-1}[/tex]* for the results:
.7042
1.1972
1.9014
None of these answers are correct :/
Any and all help is greatly appreciated!
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