# Electrodynamics- combination of resistors

1. Apr 3, 2013

### othonmp

1. The problem statement, all variables and given/known data
What is the compensative system of this combination of resistors?
http://img545.imageshack.us/img545/6610/circuitoi.jpg [Broken]

Last edited by a moderator: May 6, 2017
2. Apr 3, 2013

### dinospamoni

I'm not sure what you're referring to. Do you mean the total resistance?

3. Apr 3, 2013

### Staff: Mentor

Can you define "compensative system"? I don't recognize the term.

Last edited by a moderator: May 6, 2017
4. Apr 3, 2013

### othonmp

Yes,I mean the total resistance =]
sorry, English is not my first language

5. Apr 3, 2013

### Staff: Mentor

Okay. What techniques have you learned about for reducing (simplifying) resistor networks? Can you spot any opportunities to apply them in the given circuit?

6. Apr 3, 2013

### dinospamoni

I'd go for

series: R_total = R_1+R_2+R_3+...

Parallel" 1/R_total = 1/R_1+1/R_2 +1/R_3 +...

Be careful about which one you use

7. Apr 3, 2013

### othonmp

I know about combinations in parallel and in series, I could spot the parallel combination on the superior right corner (9Ω,8Ω,5Ω), they can be reduced to a resistance of aproximately 2.29Ω
there is a combination in series(8Ω,2Ω) that is equal a resistance of 10Ω
as well, there is a combination in parallel near B(2Ω,2Ω) that is equal 1Ω
but it just this, I don't know what I have to do with the first part, where theres are 5Ω resistances and a 9Ω resistance

8. Apr 3, 2013

### dinospamoni

Ok good so far. First, look for resistors in series and combine them into one resistor. Then see where that one is relative to the others

9. Apr 3, 2013

### Staff: Mentor

Yes, you should replace those parallel and serial resistances with their reduced values as you've stated, and continue to combine any more such opportunities that arise from those reductions.

Regarding the grouping in the top left corner near A, note the wire that bridges the combination. Since it's a perfect conductor, its resistance is zero. That ties together the points A and A'. What then must be the resistance between A and A'?

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10. Apr 3, 2013

### othonmp

So this first part can be disregarded and I just have to combine in parallel 2,29Ω with 8Ω+2Ω+1Ω

then the result would be aproximately 1,9Ω, is that right?

11. Apr 3, 2013

### Staff: Mentor

Yes, that's the right procedure

12. Apr 3, 2013

Thank you =]