# Homework Help: Thevenian theorem

1. Jan 26, 2009

### 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.

#### Attached Files:

• ###### Thevenian.bmp
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256 KB
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111
2. Jan 27, 2009

### Staff: Mentor

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.

3. Jan 29, 2009

### roshan2004

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

4. Jan 29, 2009

### 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.

#### Attached Files:

• ###### thevenian.bmp
File size:
296.2 KB
Views:
111
5. Jan 29, 2009

### Staff: Mentor

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.

6. Jan 31, 2009

### roshan2004

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

7. Jan 31, 2009

### Staff: Mentor

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

8. Feb 1, 2009

### roshan2004

Can you give some more hint please........

9. Feb 3, 2009

### Staff: Mentor

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