# Equivalent resistance

Discussion in 'Homework Help' started by gicode0823, Feb 19, 2012.

1. ### gicode0823 Thread Starter Member

Feb 8, 2012
31
0

(a) Find equivalent resistance respect to terminals A and B.
(b) Find equivalent resistance respect to terminal A and C.

redrew the diagram using iCircuit app

First I counted the all the node (8 nodes)

In series:
31 + 25 = 56Ω
38 + 29 = 67Ω

then I redrew the diagram

parallel:
67//26//39//23 = 6.65Ω
26//30 = 13.93Ω
32//34 = 16.48Ω

I redrew again

21 + 6.65 = 27.65
24//32//27.65 = 9.17

Now I saw that the 16.48 resistor is shorted

I redrew again
27//32 = 14.64
13.93 // 56 = 11.15

11.15 + 37 = 48.15

48.15//14.64//9.17 = 5.04 Ω

But the answer for part (a) is 13.07Ω.

I can't seem to find the error in my computation...

2. ### steveb Senior Member

Jul 3, 2008
2,431
469
It looks like you have a typo in your first schematic. The 34 ohm resistor was written as a 31 ohm resistor. I'm guessing that's not the only mistake, but I'll look further.

3. ### steveb Senior Member

Jul 3, 2008
2,431
469
The 16.48 ohm resistor shouldn't be shorted.

4. ### gicode0823 Thread Starter Member

Feb 8, 2012
31
0
I understand now that 16.48 ohm resistor shouldnt be shorted... but still not getting the right answer. Will redo this problem again...

5. ### gicode0823 Thread Starter Member

Feb 8, 2012
31
0
31 + 25 = 56

38 + 29 = 67

23//36//39//26//67 = 6.65

26//30 = 13.93

32//34 = 16.48

33//27 = 14.85

R1 = 24
R2 = 21
R3 = 6.65
R4 = 16.48
R5 = 14.85
R6 = 37
R7 = 13.93
R8 = 56
R9 = 35

14.85 + 37 = 51.85

51.85//13.93 = 10.98

10.98 + 56 = 66.98

16.48//66.98 = 13.23

21 + 6.65 = 27.65

13.23 + 24 = 37.23

Other two tries, I got 53.02550844 ohms...

Can't find the error...

Last edited: Feb 20, 2012
6. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
790
Almost correct.

Rab=24||(13.23+(35||27.65))=13.065Ω

gicode0823 likes this.
7. ### The Electrician AAC Fanatic!

Oct 9, 2007
2,710
494
It looks to me like Rac is not going to work out so nicely. I think a delta-wye transformation may be necessary. Anyway, for reference, I get Rac = 26.2607

gicode0823 and t_n_k like this.