# Homework Help: Elementary Linear Circuits - Dependent Sources

1. Aug 27, 2014

### Devtycoon

1. The problem statement, all variables and given/known data

the problem is a circuit analysis. I can try to make the circuit but the image i created shows all the resistors and voltage sources.

imgurl

Find i,v,is,vs

2. Relevant equations

$\sum$loop vi=0
$\sum$node ij=0

3. The attempt at a solution

I can not make a voltage loop as of yet. That would be my first attempt. Each node that I make an equation for results in more variables than what I have equations for. I am stuck on a very fundamental level here I think.

Last edited: Aug 27, 2014
2. Aug 27, 2014

### Staff: Mentor

Hi Devtycoon. Welcome to the Physics Forums.

You don't have the right URL to display your pic. Let me fix that .....

3. Aug 27, 2014

### Staff: Mentor

What are some of the equations you've been writing down?

4. Aug 27, 2014

### Devtycoon

KCL for each node. I know there is a amperage going into/out of the 3 ohm resistor that I can not account for. I uploaded some work I have done with better images this time.

5. Aug 27, 2014

### Devtycoon

I also can't find a good place to put my ground. Placing my ground in different places will change my equations.

6. Aug 27, 2014

### Staff: Mentor

We don't need a whole panoply of images! One would be ample, with relevant notations added.

First step: how do you decide the direction to mark the current in the 4 Ω resistor?

7. Aug 27, 2014

### Devtycoon

My convention I want to stick to is assume that current flows from positive to negative terminal

Last edited: Aug 27, 2014
8. Aug 28, 2014

### Staff: Mentor

Well, you won't get far if you don't assume that!

So, in what direction will the current be through the 4Ω resistor?

9. Aug 28, 2014

### Staff: Mentor

You don't need a ground, but you can consider the lowest horizontal wire as ground if you wish.

10. Aug 28, 2014

### Devtycoon

I will have the current going from the top of the 4Ω resistor (positive terminal) down through the bottom (negative terminal)

11. Aug 28, 2014

### Devtycoon

So the positive terminal of the battery is connecting to the ground? Sorry, I am new to circuits.

12. Aug 28, 2014

### Staff: Mentor

Sure! It doesn't care where you call ground.

You don't need ground, so maybe leave it out if it's going to confuse you.

Now, some of these equations .....?

13. Aug 28, 2014

### Staff: Mentor

Correct. I asked because one of the pics you posted earlier seemed to show current going the other way.

14. Aug 28, 2014

### Devtycoon

Ya I messed that up. I will begin at the node with 2i going in and i going out. It seems that I overlooked this situation. If 2 i is going in and i is going out then the 3 ohm resistor must have 1i going into that to have a KCL law satisfied.

15. Aug 29, 2014

### Staff: Mentor

Right.

16. Aug 29, 2014

Right.