Why my solutions are wrong for this circuit problem?

[PainterGuy]

Hi,

I'm sorry for the poor handwriting in the attached scan. I need to find I₂ and V_ab. I'm more than sure that my solutions are wrong. But don't know where I went wrong. I started with L1 on the left. I assumed the current in the L1 as I₁=3A as supplied by the current supply. Then applied KVL where I assumed overall voltage to be 0V. While applying KVL on L1 the current through R₁=3 ohm is I₁-I₂. Will someone please tell me what goes wrong there? Many thanks for your help.

http://img84.imageshack.us/img84/3064/i2andvab.jpg

 

[Zryn]

I started with L1 on the left. I assumed the current in the L1 as I1=3A as supplied by the current supply. Then applied KVL where I assumed overall voltage to be 0V. While applying KVL on L1 the current through R1=3 ohm is I1-I2

When doing KVL around L1 on the left keep in mind that you're trying to find the current, but you already have it. Its just I1=3A! All you need to do is get an equation that ties the L1 current and the L2 current together, and that's the current through the R1 resistor I(R1) = I1 - I2.

If you really want to do KVL you have to include an unknown voltage for the current source, which is undesirable as it introduces another variable.

Also if I2 = 3A and I1 = 3A then I(R1) = 0 as there's no current going through the 3R resistance, which doesn't sound reasonable.

Do you have a known answer you are working towards?

 

[PainterGuy]

Zryn, many, many thanks for all this help. You are so nice. Sorry, I'm little late with my thanks. :)

Cheers