# Find equivalent resistance in this circuit

## Homework Statement

http://session.masteringengineering.com/problemAsset/1515645/4/Steif.ch02.p28.jpg
Find the equivalent resistance between node A and B, knowing that Rab = Vab/Iab

## Homework Equations

KCL and KVL, I know.

## The Attempt at a Solution

There is nothing in series or parallel here, so what I did is set up KCL equations and KVL loop equations (top and bottom loops), so 6 equations with 6 unknowns and I can find Iab. I don't know how to find Vab though...

gneill
Mentor
You don't find Vab, you stick a voltage source there (value of your choosing, or just leave it as a variable, "Vab"). The equivalent resistance Rab is given by the ratio Vab/Iab.

Presumably the Vab variable will cancel out in the workings leaving you with an expression for Rab in terms of R alone.

I'm still confused though, is my method of finding Iab correct?

gneill
Mentor
I'm still confused though, is my method of finding Iab correct?

Well, the approach of finding Iab given a source voltage Vab is correct. But you haven't shown the details of your work so it's not possible to say more.

CWatters
Homework Helper
Gold Member
I'm still confused though, is my method of finding Iab correct?

You don't need to solve the equations to find Iab or Vab their own.

Rab = Vab/Iab

so reaarange the equations until you get one for the ratio Vab/Iab in terms of the resistors only.