Thevenin Eq. with controlled current source

[novatank]

Hi!

So, I've got this problem, and it's doing my head in a bit;

http://yfrog.com/mtthevcsj

I'm not entirely sure where to begin with this one. I've tried a few things, and hit dead ends pretty quickly on all of them; trying to find vx, Voc, Isc, node analysis by treating terminal 'a' to the Current source/8ohm/4ohm junction as one node.

Am I right in thinking that Voc = V across the 8ohm resistor?
Also, I read somewhere that the controlled current source may be treated as an open circuit, is this right?


If some one could please give me a shove in the right direction, I'd be extremely grateful.

Thanks in advance!
Tank

 

[samdunhamss]

Dependant Current Sources may NOT be treated as open circuits, but in thevenin and norton equivalents independent sources may be considered as such.
First off, this circuit contains both independent and dependent sources. Apply KVL or KCL and then you'll find the the voltage across your 4 ohm resistor. KCL is a powerful tool in these types of problems. That will be a good step in the right direction, also, keep ohm's law in mind in relation to your short circuit current and your open circuit voltage, what might their ratios represent?