## TomLikesPhysics 2 years ago How do I find the total resistance of this network? Somehow I can not figure this simple network out.

1. TomLikesPhysics

2. TomLikesPhysics

I know how to deal with resistors that a parallel or in a row but this configuration somehow confuses me.

3. TomLikesPhysics

Hmmmm I ended up with 50/3 Ohms for the total resistance.

4. henpen

Given that R3=R4, I think no electrons will flow down resistor 5.

5. TomLikesPhysics

But R5 is not as big as R3 so woudn´t some electrons prefer R5 over R3?

6. henpen

But they 'know' (because of repulsion of electrons in front of them, possibly) that R4 exists.

7. eSpeX

To find the equivalent resistance for this circuit you need to do a delta|wye conversion and then do your calculations.

8. TomLikesPhysics

I have never heard of a delta wye conversion.

9. Mashy

tommy.. this network indeed is very complicated and you need to do a delta conversion .. however if R1/R3= R2/R4 then the its called a balanced circuit.. and it can be proved that.. no current flows through R5 and you can chuck it!

10. TomLikesPhysics

Ok, but this network ist not a balaced circuit because that resistor-ratio does not fit this network.

11. Vincent-Lyon.Fr

Use Δ→Y transform (fast), or use 2 loops and write down all Kirchhoff's circuit laws that apply (slow). http://en.wikipedia.org/wiki/Delta_Y

12. Vincent-Lyon.Fr

You can also remove R5 and use Thevenin's equivalent to find the fictitious generator between those terminals, then put R5 back in again. But this is longer.

13. ghazi

using thevnin will give the load voltage and i don't think we can apply thevnin here, if you remove R5 then yes we can think of it

14. TomLikesPhysics

Okay, I used Kirchhoff and got now this:

15. Mashy

ok this is out of my league now :D

16. ghazi

i guess its 300/11 ohm =27.27 ohm

17. TomLikesPhysics

Are my equations alright?

18. Vincent-Lyon.Fr

Answer is 685/24 = 28.54 Ω.

19. Vincent-Lyon.Fr

There is a mistake : J5 cannot have a minus sign in eq.1 and eq.2

20. Vincent-Lyon.Fr

Besides, I do not understand what UR means. Are you multiplying resistance with voltage? This will not lead you anywhere.

21. TomLikesPhysics

-.- of course. My mistake, the Us have to be Is. For the Equations one and two I was looking at the nodes in the middle.