Solve I(x) in the current using supermesh concept?

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The discussion focuses on solving for the current I(x) using the supermesh concept in circuit analysis. Initial equations were set up for multiple meshes, and Cramer’s rule was applied to find I2 and I3, resulting in I2 = -4.08A and I3 = -0.08A. However, a mistake was identified in treating the current source, leading to a reevaluation of the mesh equations. After correcting the approach, the final calculations yielded I3 = 1.75A and I(x) = -1.75A. The importance of accurately interpreting current sources in mesh analysis is emphasized.
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Homework Statement


30k6kqt.png


Homework Equations


1111lqw.png

4A = I3 - I2 (supplementary eq.)

Mesh 1:
6(I1)-6(I2)=2A

Mesh 2,3 (supermesh):
6(I2-I1)+6(I2-I4)+12(I3)=0
-6(I1)+12(I2)+12(I3)-6(I4)=0
substitute supp. eq.:
-6(I1)+12(I2)+12(I2+4A)-6(I4)=0
-6(I1)+24(I2)-6(I4)=-48

Mesh 4:
6(I4-I2)=-3A
-6(I2)+6(I4)=-3A


The Attempt at a Solution


|6 -6 0| |I1| = | 2 |
|-6 24 -6| |I2| = |-48|
|0 -6 6| |I4| = | -3|

used cramer's rule (not sure if there was an easier way) and used online matrix calculator http://ncalculators.com/matrix/matrix-determinant-calculator.htm cause i was lazy :(

I2 was all i needed to calculate:
I2 =-1764/432= -4.08A

supp. eq.:
4A+I2=I3
I3= -0.08A

since I(x) is opposite to I3, i got I(x)=0.08A as my answer.
 
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asdf12312 said:

Homework Statement


30k6kqt.png


Homework Equations


1111lqw.png

4A = I3 - I2 (supplementary eq.)

Mesh 1:
6Ω(I1_Amps)-6Ω(I2_Amps)=2Amps

Mesh 2,3 (supermesh):
6(I2-I1)+6(I2-I4)+12(I3)=0
-6(I1)+12(I2)+12(I3)-6(I4)=0
substitute supp. eq.:
-6(I1)+12(I2)+12(I2+4A)-6(I4)=0
-6(I1)+24(I2)-6(I4)=-48

Mesh 4:
6Ω(I4_Amps-I2_Amps)=-3Amps
-6(I2)+6(I4)=-3A


The Attempt at a Solution


|6 -6 0| |I1| = | 2 |
|-6 24 -6| |I2| = |-48|
|0 -6 6| |I4| = | -3|

used cramer's rule (not sure if there was an easier way) and used online matrix calculator http://ncalculators.com/matrix/matrix-determinant-calculator.htm cause i was lazy :(

I2 was all i needed to calculate:
I2 =-1764/432= -4.08A

supp. eq.:
4A+I2=I3
I3= -0.08A

since I(x) is opposite to I3, i got I(x)=0.08A as my answer.

Right away I see a problem in the two equations I've marked in red. I inserted some units and I don't think it's working out very well, is it?

The equation for mesh 1 should be I1_Amps = 2_Amps and similarly for mesh 4.
 
i see my mistake now. i was trying to treat the current source as a voltage source but that's defnitely not right. so the equations are:

I1=2A
I4=-3A

so now this makes everything much simpler. all i need now is the supp. eq. and the eq. for the supermesh:

4A = I3 - I2
-6(I1)+12(I2)+12(I3)-6(I4)=0
-6(2A)+12(I2)+12(I3)-6(-3A)=0
12(I2)+12(I3)=-6V
12(I3-4A)+12(I3)=-6V
24(I3)=42
I3=1.75A
I(x)=-1.75A
 
Last edited:

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