# Mesh eqs

Discussion in 'Homework Help' started by n_adam, Apr 4, 2014.

1. ### n_adam Thread Starter New Member

Mar 1, 2014
19
0
Hi guys,

I need to solve this problem with the mesh current method. I am having trouble figuring out the three equations for the three loops. What confuses me is the current source and that the voltage is unknown across it. Any help or hint would be highly appreciated.

File size:
22.8 KB
Views:
20
2. ### shteii01 AAC Fanatic!

Feb 19, 2010
3,968
616
Ok. You did first step. Define the problem.

Next step is to draw mesh currents. Go do that and post a picture.

3. ### n_adam Thread Starter New Member

Mar 1, 2014
19
0
here are the mesh currents

File size:
263.4 KB
Views:
24
4. ### n_adam Thread Starter New Member

Mar 1, 2014
19
0
and the three equations I came up with

File size:
283.2 KB
Views:
19
5. ### shteii01 AAC Fanatic!

Feb 19, 2010
3,968
616
Ok.

Now. Look at i1. Do you see that i1 enters the current source and exits the current source?

6. ### n_adam Thread Starter New Member

Mar 1, 2014
19
0
Yes, so i1 = 0.01A I assume

7. ### shteii01 AAC Fanatic!

Feb 19, 2010
3,968
616
Yes. i1=10 mA.

However. In the future you have to examine these things carefully. Current has magnitude and direction. In your case the magnitude is 10 mA. We assume clockwise direction of i1 means that i1 is positive. So we look at the direction of the current from the current source, it matches the direction of i1. So i1=10 mA.

However. If direction of current source was opposite of i1, then i1 would have been -10 mA. Meaning that magnitude of i1 is 10 mA, but its assumed direction is wrong which we indicate by the negative sign.

8. ### n_adam Thread Starter New Member

Mar 1, 2014
19
0
Ok thank you I got the right answer.

9. ### n_adam Thread Starter New Member

Mar 1, 2014
19
0
I have an other problem I can't figure out. I am sure I am really close to the solution but something is not right. Would you mind taking a look at what I have so far?

File size:
14.7 KB
Views:
16
File size:
309.9 KB
Views:
15
File size:
304 KB
Views:
11
10. ### shteii01 AAC Fanatic!

Feb 19, 2010
3,968
616
Use mesh current. You have 3 meshes. You will have three mesh currents. The current in left mesh and current in center mesh will have to be solved for. The current in the right mesh is going to the be current of the current source, but watch the direction of the mesh current, the mesh current will point down, the current source current points up, that means mesh current will be -28 A.

Now find the other two mesh currents. Then find the voltages v2 and v3 using Ohm's Law.

11. ### n_adam Thread Starter New Member

Mar 1, 2014
19
0
the book specifically asks for node voltage method..