In summary, when looking to find the Thevenin equivalent for the circuit in pic. 1, you need to find the open circuit voltage at a-b, and the Thevenin resistance "looking into" a-b. There are no immediate opportunities to combine resistances in either series or in parallel, so serial configurations are not available, and while some components share a node at one end, at the other they have another component situated between their connections, so no parallel configurations are possible. You should be trying to find the output voltage at a-b, and then the equivalent resistance at a-b with all the sources suppressed (which means shorting voltage supplies and removing current supplies).
Yes. Be sure that you pay attention to the polarity of the voltage source. Remember that you found a negative value for E, making point a negative with respect to b.
Remember that you found a negative value for E, making point a negative with respect to b.
I need to change the direction of E?
But E>0 because I3>0 & R3>0.
One of the tasks is done(I don't sure in this tense form)(another task is node potential method(only 2 nodes in the circuit so I try to make on my own(with rare success)).Thanks for your help.