I have been given a question for homework and I think you have to use Thevenin's Theorem to answer it but I'm just not sure what to do. Maybe there is also a way of working it out without Thevenin's. I've only just learnt the theorem recently so I'm not very confident with it.

Here is the question:
In Figures (a) & (b), find Vab. [Answers: 4.2V; 7.2V]

 

hi John.
Welcome to AAC,
As this is Homework, please post your best attempt at solving , we can then help you.
E

 

That's as far as I got (see attachment)

You're starting off on the wrong foot because you are throwing an equation at a problem when it doesn't apply.

You are using the current division formula for two resistors in parallel; the problem is that the two resistors aren't in parallel.

You certainly don't HAVE to use Thevenin's Theorem to solve these problems. The issue is whether you are required to because of the instructions on the assignment. If it's not required, then just analyze them like any other problem, perhaps using nodal analysis or mesh current analysis.

 

I think you have to use Thevenin's Theorem to answer it

The given circuit has the appearance of a Norton equivalent connected to a Thevenin equivalent. What if you did a direct conversion of the Norton to a Thevenin form and then analyzed that?