deta-wye configuration of resistors

[PG1995]

Hi

I was having a look on the "Example 2.15" which you can see in the following link: https://img23.imageshack.us/img23/5218/deltawye.jpg

1: I don't understand how "abn" form a delta configuration. For example, take the case of "can" configuration. We start at 'c' and traverse through 12.5Ω resistor toward 'a', and then from 'a' we traverse through 10Ω and 5Ω resistors and end up at 'c' where we started the traversing. It is a "can" delta configuration. But what is happening in case "abn" deta - which in my view is not a delta? Please help.

2: Now consider the statement which I have highlighted: Another approach would be to solve for the equivalent resistance by injecting one amp... Chap 4.

In Chap 4, which we haven't covered so far, the author introduces these topics: Linearity Property, Superposition, Source Transformation, Thevenin's Theorem, Norton's Theorem, Maximum Power Transfer.

Which of the above theory/topic the author would have used to solve the problem in "Example 2.15" instead of detal-wye appraoch? Please tell me.

Thank you for your help and time.

 

[BradtheRad]

The author is referring to the toolbag of tricks that can be used to do these math problems.

Point 2 in your post refers to the experiment of seeing what voltages develop across a resistance when a known current goes through it. (V = IR) If this kind of working in reverse yields a usable result, then scale it up or down so that you arrive at the specified 120 V supply.

Another trick is to try pretending this or that component isn't there. (Example, the 5 ohm in the middle.) This may enable you to spot a tactic which could become a step to finding the solution.

Another trick for solving an unknown node is to locate another node whose position resembles the first and which is situated among voltages which are known.

Etc.

At this point the author expects you to demonstrate you can use the method taught in the chapter.

 

[_Eduardo_]

1: I don't understand how "abn" form a delta configuration. For example, take the case of "can" configuration. We start at 'c' and traverse through 12.5Ω resistor toward 'a', and then from 'a' we traverse through 10Ω and 5Ω resistors and end up at 'c' where we started the traversing. It is a "can" delta configuration. But what is happening in case "abn" deta - which in my view is not a delta?

abn :
Rab = 30ohm
Rbn = 20ohm
Rna = 10ohm

2: Now consider the statement which I have highlighted: Another approach would be to solve for the equivalent resistance by injecting one amp... Chap 4.

In Chap 4, which we haven't covered so far, the author introduces these topics: Linearity Property, Superposition, Source Transformation, Thevenin's Theorem, Norton's Theorem, Maximum Power Transfer.

Which of the above theory/topic the author would have used to solve the problem in "Example 2.15" instead of detal-wye appraoch? Please tell me.

I don't know the methods and tricks covered in Chap4, but the meaning is what you can solve applying general methods, not by resistance transformations.
The best way is applying the "Node voltage method" or "Mesh current method"


The image is an aplication of NVM.
Just write the matrix and solve "by hand" or "by soft" :grin:.

Req_ab = 9.6316 ohm