Kirchhoff's laws question circuit?

[Questions999]

Homework Statement

I have the circuit in the figure.I have to find i1 and R

Homework Equations

I am thinking about applying the division of the current and any of the K's laws but I don't know where to start.Can you pleas give me a hint?

The Attempt at a Solution

I tried to find the voltage in the 4 Ohm resistance and it is 8 Volt.Since 4 oHm is in parallel with 8 Ohm ,then their voltage equals.This is how far I have got.
http://i.imgur.com/FoQmlFl.jpg?1?3770

 

[gneill]

I tried to find the voltage in the 4 Ohm resistance and it is 8 Volt.Since 4 oHm is in parallel with 8 Ohm ,then their voltage equals.This is how far I have got.

Find the current through the 8Ω resistor. What new current can you label on the diagram?

 

[Questions999]

It's 1 A.Does that mean that the current through R is 3A?

 

[gneill]

It's 1 A.Does that mean that the current through R is 3A?

Yes. Where does the 3A come from (what other current must be 3A)?

 

[Questions999]

The one running through 2 Ohm?

 

[gneill]

The one running through 2 Ohm?

Yes and no. Certainly the 3 A flows there, but i₁ also flows through that resistor. Can you place the 3 A on the appropriate wire leading from the node? Any ideas what you might do with that knowledge?

 

[Questions999]

I want to find the current in 2 Ohm so I can apply the K's law in the nod...but I don't know how

 

[gneill]

I want to find the current in 2 Ohm so I can apply the K's law in the nod...but I don't know how

Suppose that you happened to know the potential of that node. Would you be able to find that current then?

 

[Questions999]

yes.This sounds like a puzzle.I'll have a look at it myself later.Thank you anyway.

 

[gneill]

yes.This sounds like a puzzle.I'll have a look at it myself later.Thank you anyway.

Good idea

As a hint, consider applying nodal analysis at the node (KCL with a bit of KVL thrown in )

 

[Questions999]

O mi god that's what I want thinking! Thanks a lot mate!