# Equivalent resistance of circuit

#### Learnphysics

1. Homework Statement

Find the equivalent resistance between terminals A and B for this circuit:

http://img716.imageshack.us/img716/1121/1035p.png [Broken]

[PLAIN]http://img716.imageshack.us/img716/1121/1035p.png [Broken]

2. Homework Equations

I know how to add resistances in parralell and series, it's just that i can't figure out which ones are connected in parralell and which ones are in series

3. The Attempt at a Solution

It kind of appears that the 20 ohm and 30 ohm resistors are in series, and that 60 ohm and 40 ohm resistors are in series.

But i have no idea.

A parralell connection is one which has both ends of an element directly connected to another. This appears to be true for the 20 and 30 ohm resistors. And also for the 60 and 40 ohm resistors. But where in the circuit would i place their equivlent resistances?

So i guess the question i'm asking is more to do with how to identify which ones are parralell and which ones are in series

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#### tiny-tim

Homework Helper
Hi Learnphysics!

With a wire of zero resistance, you can ignore the wire and treat the two endpoints as the same point …

in this case, that makes a sort of figure-of-eight with "a" in the middle …

that should make it clear

#### Learnphysics

Hi Learnphysics!

With a wire of zero resistance, you can ignore the wire and treat the two endpoints as the same point …

in this case, that makes a sort of figure-of-eight with "a" in the middle …

that should make it clear
Thank you!

The equivalent resistance i got is 9.6 ohms which seems to work out.

Staff Emeritus
Homework Helper

#### JasonSola

Sry but i still dont get it..mind to explain in more detail(how to know they are parallel or series to each other)?

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