# Duality(electric circuits)

1. Sep 2, 2012

### Avichal

I just do not understand this concept. My book doesn't explain it clearly nor do I find anything useful on Wikipedia.
So what is it used for? I know the steps to convert - like changing voltage source to current source, resistor to conductor etc. But why am I doing it? What is the use?

2. Sep 2, 2012

### davenn

I have no real idea what you are referring to .... a resistor is already a conductor

can you give a specific application of this "duality" you refer to please :)

Dave

3. Sep 2, 2012

### Studiot

Are you referring to Thevenin and Norton's theorems?

4. Sep 2, 2012

### Avichal

Here is the link. I don't think it is an important topic hence so less resources available

5. Sep 2, 2012

### Avichal

I am also looking for its application :)

6. Sep 2, 2012

### Studiot

Well your not important pages states most of the important formulae in electrics.

Every one of those formulae are vitally important.

What exactly did you want to know?

7. Sep 2, 2012

### Avichal

Well I encountered some questions where I have to convert circuit into its dual. So basically what I am asking is the use of converting a circuit into its dual.

8. Sep 2, 2012

### dlgoff

I've never heard it called "duality" but he must mean, Thévenin's theorem and it's extension Norton's theorem.

9. Sep 2, 2012

### Studiot

dlgoff,
Have you looked at the link provided by the OP?

Yes Norton's and Thevenins theorems are duals of each other as are for instance wye - mesh transformations.

10. Sep 2, 2012

### dlgoff

I have now.

11. Sep 3, 2012

### 256bits

Nowadays, mainly to increase your understanding of system behavior, such as a parallel RC and and series RL circuit being duals of each other, where current and voltage will behave similarily from one to the other. Resitance -> conductance, inductance -> capacitance, parallel -> series, voltage source -> current source and vice-versa.

You might want to look up analog systems, where the behavior of a mechanical system can be modelled as an electrical system ( also valid for thermal, mechanical, electrical, fluid ).

The analog, dualog was used extensively many years ago since electrical systems could be more readily made from components and system behavior observed. Resisters, capacitors, inductors could easily exchanged to vary system behavior. Try that with not so readiy available components for a mechanical system. A mechanical system could be modelled as electrical and observed. Thevin and Norton could readily be applied.

The advent of the analog and then the digital computer has depreciated this type of analysis, but it is still interesting to know how systems relate to one another.