# Help on thevenin and norton equivalents

1. Mar 26, 2012

### euphoria172

Hi, i need help on this question. Anyone can show me a step by step method. Thx.
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

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• ###### Thevenin and Norton equivalents.jpg
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2. Mar 26, 2012

### tiny-tim

welcome to pf!

hi euphoria172! welcome to pf!

show us what you've tried, and where you're stuck, and then we'll know how to help!

3. Mar 26, 2012

### euphoria172

Thx for the kind invitation.
I have tried the question but unsure of the answers.
I am also confuse on the parallel part of the circuit.

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4. Mar 26, 2012

### Staff: Mentor

Why do feel that your Method 1 is incorrect? The results look fine It appears that you first found the Thevenin equivalent of the voltage source and first two resistors and then applied superposition to find the final Voc. Nothing wrong with that.

In your Method 2, it's not entirely clear to me what your steps were trying to accomplish. It appears that you were again trying to use superposition to find the contribution from each source, but for the voltage source you found the total current that it produces, not the portion flowing through the shorted output.

The method that you employed in the first attempt, namely working section by section through the circuit making Thevenin (or Norton) transformations can be very useful. It can allow you to combine sources easily as you go. Try it for the Norton equivalent: first convert the 25V source and 5 Ohm resistor to its Norton equivalent. What's then in parallel and can be combined? Rinse, repeat

5. Mar 26, 2012

### euphoria172

Thx gneill. I realise i make a mistake on a similar question that cause me to doubt this answer.
Thx again. I appreciate your help.