# Equivalent electrical resistance

1. Feb 17, 2013

### TheDoctor46

Hello guys!

It's been a while since I last had to deal with direct current and I'm having a hard time solving the equivalent resistance for a simple circuit.

I know this is rather simple, but I can't find my notes, so, could you please help me?

The photo of the circuit is attached.

Thanks a lot!

#### Attached Files:

• ###### Resistance.jpg
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Last edited: Feb 17, 2013
2. Feb 17, 2013

### TheDoctor46

I am able to calculate the parallel resistors, but I can't remember how to proceed for the last group.

Thanks!

3. Feb 17, 2013

### Staff: Mentor

Which resistors did you find that are in parallel?

4. Feb 17, 2013

### TheDoctor46

I highlighted the part that I am interested in finding.

Thanks!

#### Attached Files:

• ###### Resistance highlight.jpg
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5. Feb 17, 2013

### Staff: Mentor

Are there opportunities for parallelism there? How can you tell if resistors are in parallel?

Hint: The placement and angles at which components are drawn on a diagram are irrelevant; it's the topology that counts (what's connected to what). Connections can be bent, twisted, and moved anywhere along a given wire without changing the circuit.

6. Feb 17, 2013

### TheDoctor46

Yes, I know that, but I am not able to calculate the equivalent resistance of the highlighted part. I know that the angles in the diagram don't matter, but I can't tell how the resistors are arranged.

7. Feb 17, 2013

### haruspex

Since only the topology matters, you can slide the junctions around on the wires as long as you don't slide past any components. Can you see how to do this in a way that reduces the number of junctions in the highlit part?