Homework Help: Creating Circuits with equivalent resistances

1. Mar 21, 2013

ragsz

1. The problem statement, all variables and given/known data
Given 4 Identical resistors, I need to be able to find the 9 combinations of circuits with equivalent resistances

2. Relevant equations
Do I just keep flipping between parallel resistor sequences?

3. The attempt at a solution
I drew 3 different circuits that I believe to be correct, but cannot seem to come up with 9 different ones.

2. Mar 21, 2013

Staff: Mentor

Welcome to the PF.

Could you clarify the problem statement some? What do you mean by "equivalent resistances"? Equivalent to what? To one of the single R values? Or equivalent to some other value, and all 9 combinations are equivalent to that value?

3. Mar 21, 2013

ragsz

Maybe I should have typed it word for word... my bad. And thanks for the reply
You are given for identical 300 ohm resistors. Find as many ways of connecting all four resistors that give unique equivalent resistances. Then my professor gives us a hint that we should get 9 different arrangements using all four resistances that will give unique equivalent resistances.
Thanks

4. Mar 21, 2013

Staff: Mentor

Oh, unique equivalent resistances. So each configuration will result in a different equivalent resistance, and you have to use all 4 resistors in each configuration. Got it.

Show us what you have so far, and maybe we can offer some hints...

5. Mar 21, 2013

Staff: Mentor

I'm at 5 right now.... Interesting problem.

6. Mar 21, 2013

Staff: Mentor

7...

7. Mar 21, 2013

Staff: Mentor

9.

How's it going on your end?

8. Mar 21, 2013

ragsz

9. Mar 21, 2013

Staff: Mentor

You probably don't have to draw the battery, just show the resistors with the connection points at the ends of the configuration. Unless the problem asks for you to show the battery for some reason.

So what you have shown so far is:

4R = R + R + R + R

R = R/2 + R/2

Now keep going. Try different combinations and connections, and see if they result in a different equivalent resistance. It's actually kind of fun...