Solve Thevenian Theorem: Calculate Voltage Across A and B

[roshan2004]

This question is based on the thevenian's theorem,but my problem is on the basic rule of circuit.I have come at the stage where I have to calculate the Thevenian's voltage that is "V" across A and B.I know that V=I*6 since V across AB equals to the V across CD as there is no drop of current on the 3 ohms resistor but now I have to calculste I which can be found by V/R(total).V is 36 volt.Now I have to find Total R which is the stage where I am totally confused since I just know how to rearrange the given circuit.I don't know which one is parallel or in series with another.Please have a look on the picture (which is messy).
Your post is valuable or me.

 

[Doc Al]

The Thevenin voltage is the open circuit voltage between the terminals A & B. Since you already realize that the 3 Ω resistor is irrelevant, just ignore it. You have a simple series circuit, for which you can find the total resistance and then the current. Use that to find the Thevenin voltage.

 

[roshan2004]

Thanks,I used the voltage divider rule and got the answer.

 

[roshan2004]

This is another type of question where I am troubled to calculate the thevenian voltage.The original question is to calculate the current through 10 ohms resistor.

 

[Doc Al]

Once again, the Thevenin voltage is the open circuit voltage between A and B. That means there's no current through the 8 Ω resistor (but don't neglect the 12 V battery). Use the voltage divider rule to find the voltage across the 2 Ω resistor.

 

[roshan2004]

Yeap I really don't know how to treat 12 V battery.

 

[Doc Al]

Yeap I really don't know how to treat 12 V battery.

It's in series with the Thevenin voltage. (But oppositely oriented.)

 

[roshan2004]

It's in series with the Thevenin voltage. (But oppositely oriented.)

Can you give some more hint please...

 

[Doc Al]

Do this: Find the Thevenin voltage just before the 12 V battery. Then you can add the 12 V battery in series with it.