# Mesh Analysis for time domains?

• Engineering

## 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:

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:

Am I missing something here?
Thanks

Delta2

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Delta2
Homework Helper
Gold Member
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)?

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.

Delta2
Homework Helper
Gold Member
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 ,

Joshy
Delta2
Homework Helper
Gold Member
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.

Joshy
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)

Delta2
Homework Helper
Gold Member
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.

jisbon
Joshy
Gold Member
I agree with Delta. You draw both of the currents in the same direction and so their sign should not flip.

Delta2