# I'm having a problem solving for voltage between two points

Discussion in 'Homework Help' started by barrett50, Feb 16, 2016.

1. ### barrett50 Thread Starter New Member

Feb 1, 2016
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I'm having some problems finding the value for Vx. So far I have found the mesh current equations for all of the loops, and all that's left is Vx. Can someone help me find a starting point for this?

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2. ### shteii01 AAC Fanatic!

Feb 19, 2010
3,516
515
The fact that you can not find Vx tells me that you don't have mesh currents.
Nice try though.

3. ### WBahn Moderator

Mar 31, 2012
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So... are we supposed to use our crystal balls to see these mesh current equations that you claim to have found for all the loops?

4. ### barrett50 Thread Starter New Member

Feb 1, 2016
14
0
I didn't say I have the currents, I said I have the equations. The problem comes in at the end of my third KCL that is

8(Iy-I3) + 6(Iy-I2)+3Vx

My problem is that I don't know what I'm supposed to substitute in for Vx.

5. ### shteii01 AAC Fanatic!

Feb 19, 2010
3,516
515
What is that equal to?

6. ### barrett50 Thread Starter New Member

Feb 1, 2016
14
0
So I labeled the first box I1, upper mid box is I2, lower mid is I3, and right box is I4. There is a supermesh at I2 and I3. I go clockwise

I1 = -4 (A)

KCL at SuperMesh
3(I3-I1)-2+5(I2)+6(I2-I4)+8(I3-I4)

KCL at I4 is
8(Iy-I3) + 6(Iy-I2)+3Vx

KVL for the dependent current source is
Iy=(I2-I3)/7

7. ### shteii01 AAC Fanatic!

Feb 19, 2010
3,516
515
Anyway. Vx=2+3(whatever currents pass through the 3 Ohm resistor)

8. ### WBahn Moderator

Mar 31, 2012
18,089
4,917
These are not equations, they are expressions. Equations involve this thing called an equals sign.

Also, you need to specify which direction your mesh currents are circulating. Otherwise there is no way to know if your value for I1 is correct or not.