Mesh Analysis for time domains?

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  • Thread starter jisbon
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  • #1
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Homework Statement:

Solve the following mesh circuit.

Relevant Equations:

-
I've tried to solve the following circuit using mesh equation, but the solution seems to differ from my attempted answer.

Mesh circuit as follows:

1589772153530.png

My mesh equation is:

-10+3(i1)+2s(i1-i2)=0 (for the mesh on the left)
and
-10+12(i2)+6s(i2)+2s(i2-i1)=0 (right mesh)

However the answer seems to be different and claims that the equation are as follows:

1589772263290.png


Am I missing something here?
Thanks
 
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Answers and Replies

  • #2
Delta2
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You have to show us how you took the directions of currents ##I_1,I_2## to be

And why you say in time domain since it seems you doing it in the s-domain (Laplace transformed currents)?
 
  • #3
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Sorry, what I meant was s domain.
As shown in the diagram, I1 is in the clockwise direction, while I2 (the one on the right) is in anticlockwise.
 
  • #4
Delta2
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Then in your equations you should put ##I_1+I_2## where you have ##I_1-I_2## (or ##I_2-I_1##) and then your answer is the same with the book answer.
You should put ##I_1+I_2## because that's what we get -given the current directions as you say -if we apply KCL at the junction with the 3##\Omega## resistor the 6s coil and the 2s coil ,
 
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  • #5
Delta2
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Sorry I now understood you use mesh currents, but still the total mesh current in the branch that has the source and the 2s coil is ##I_1+I_2## because one is clockwise and the other counterclockwise.
 
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Sorry I now understood you use mesh currents, but still the total mesh current in the branch that has the source and the 2s coil is ##I_1+I_2## because one is clockwise and the other counterclockwise.
Oh I see. So if they are in the same direction, my old equations will then be correct?
This:
10+3(i1)+2s(i1-i2)=0 (for the mesh on the left)
and
-10+12(i2)+6s(i2)+2s(i2-i1)=0 (right mesh)
 
  • #7
Delta2
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Oh I see. So if they are in the same direction, my old equations will then be correct?
This:
10+3(i1)+2s(i1-i2)=0 (for the mesh on the left)
and
-10+12(i2)+6s(i2)+2s(i2-i1)=0 (right mesh)
Yes I believe the above equations are correct if both are anticlockwise.
 
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  • #8
Joshy
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I agree with Delta. You draw both of the currents in the same direction and so their sign should not flip.
 
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