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

In summary, the conversation involves solving a circuit with several meshes and a current source. After realizing the mistake of treating the current source as a voltage source, the equations are simplified to I1=2A and I4=-3A. Using the supplementary equation and the supermesh equation, the current I3 is calculated to be 1.75A and the current I(x) is determined to be -1.75A.
  • #1
asdf12312
199
1

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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  • #2
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.
 
  • #3
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:

1. What is the supermesh concept in circuit analysis?

The supermesh concept is a technique used in circuit analysis to simplify the process of solving for unknown currents in a circuit with multiple current sources. It involves combining two or more meshes in a circuit into one larger mesh and using Kirchhoff's Voltage Law to solve for the unknown currents.

2. When should the supermesh concept be used in circuit analysis?

The supermesh concept should be used when a circuit has multiple current sources that are connected in such a way that they cannot be easily analyzed individually. In this case, combining the meshes using the supermesh technique can simplify the analysis process.

3. What is the purpose of using the supermesh concept in circuit analysis?

The purpose of using the supermesh concept is to simplify the process of solving for unknown currents in a circuit with multiple current sources. It allows for the combination of multiple meshes into one larger mesh, reducing the number of equations that need to be solved.

4. How do you apply the supermesh concept to solve for I(x) in a circuit?

To apply the supermesh concept, first identify which meshes can be combined into a supermesh. Then, use Kirchhoff's Voltage Law to write an equation for the supermesh, equating the voltage drops across all circuit elements to the sum of the voltage sources. Finally, use this equation to solve for the unknown current, I(x).

5. Are there any limitations to using the supermesh concept in circuit analysis?

Yes, there are some limitations to using the supermesh concept. It can only be applied to circuits with current sources, and it does not work for circuits with dependent sources. Additionally, the circuit must have a single source of voltage or a single source of current. If these conditions are not met, the supermesh concept cannot be used.

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