# Homework Help: Help me to understand basic circuit analysis solution

1. Sep 27, 2010

### General_Sax

1. The problem statement, all variables and given/known data

2. Relevant equations
3. The attempt at a solution

I just don't understand why they went [(12||6) + 2]

I tried doing (12||8) and I ended up getting the wrong answer.

Why do you have to add the 2k(ohms) to the effective resistance of the 12||6 k(ohms)?

Why couldn't one use 12||8 ?

Another question: Is there any paticular order to calculating the effective resistance?

ie, does one have to work outside -> inside or something similiar?

#### Attached Files:

• ###### IRWIN 9e 2_52.pdf
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2. Sep 28, 2010

### skeptic2

Before beginning to work the problem it helps to redraw the circuit to simplify it, at least in your mind, as in the attachment.

It usually is best to start with the resistances farthest from the source and work back towards the source.

So in the attached circuit do you see why first the parallel combination of the 12k and 6k are calculated and then 2k is added?

#### Attached Files:

• ###### PF resistors.doc
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3. Sep 28, 2010

### General_Sax

That makes much more sense. Thanks for your time!

4. Dec 18, 2010

### evra

there is a simpler method. i.e;
solve the:
step 1: 2k//6k
step 2: 4k//12
step 3: draw the circuit equivalent whereas u will have the rest in parallel
step 4: u will get exactly 2k