Is there any algebraic proof for Thevenin's theorem?

[Benomatics]

As i profread his solution to the circuit using Thevenin myself, i want to comment on your statement meBIgguy "you seem to think thevenin equivalent can change with load" Yes i think so if i change thel oad i am considering then i will have to devise a different equivalent circuit. An on your question, you thought wrongly, you can read my previous posts, i have never at anytime said the load was part of the equivalent circuit, i am not even saying obtainig the with Thevenin's voltage and Thevenin's resistance you are unable to find the voltage across the load, but i am saying it involves finding another voltage Vth from your original voltage. Y

 

[Benomatics]

Sorry i did not complete that, you might think i do not understand Thevenin's theorem, but infact i do and i have derived, it and if you wish to confirm, i have included the document in this post. Thevenin succesfully calculates the voltage across the load, though even for for more complex circuits you will rather opt for other theories. Technically Thevenin;s theorem creates another problem to solve a problem. Changing the circuit just to suit one particular load, but forgetting that you are at the same time rendering the other resistive components inconsistent in regards to properties with the original, for the solution to the problem, i willl get back to you on what i think about it, and i am preparing a different one this time with two or more voltage sources. However i am really enjoying the contribution here.Bye for now.

 

[Averagesupernova]

I didn't think Thevenin could be this irritating. Long long ago I had an instructor ask the class for several resistor values that we wanted to use in a network and a voltage for the voltage source. I don't remember what the network was in terms of arrangement but it doesn't matter. He drew this on the board and then drew several various load resistors that could be switched in. He asked the class to find the load current and voltage for each different load. We did. None of us had heard of Thevenin. In less than half the time it took us to solve for them he solved for all of them. The reason is he used Thevenin. He found the Thevenin voltage and Thevenin resistance and simply took the load and put in series with the Thevenin resistance and solved. The Thevenin voltage and resistance stayed the same for each different load. To be honest I haven't had a lot of use for it since then but I know the laws of physics haven't changed. It certainly does have its place though.
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The theorem might be useful but it actually assumes a false state to solve a problem.

I suppose that is arguable but seriously we assume a lot of false states in engineering. As pointed out before, no one cares about what is going on inside the network, only at the port(s).

 

[donpacino]

Sorry i did not complete that, you might think i do not understand Thevenin's theorem, but infact i do and i have derived, it and if you wish to confirm, i have included the document in this post. Thevenin succesfully calculates the voltage across the load, though even for for more complex circuits you will rather opt for other theories. Technically Thevenin;s theorem creates another problem to solve a problem. Changing the circuit just to suit one particular load, but forgetting that you are at the same time rendering the other resistive components inconsistent in regards to properties with the original, for the solution to the problem, i willl get back to you on what i think about it, and i am preparing a different one this time with two or more voltage sources. However i am really enjoying the contribution here.Bye for now.

please see what me big guy said above... also thevenin is useful for evaluating how the load voltage ad current will change as the load changes.

 

[meBigGuy]

Thevenin turns out to be incredibly useful when you need a Thevenin Equivalent. Otherwise not so much.

I totally do not understand your fixation. Neither what you are fixated on, nor to what end. Thevenin is what it is.

Can you succinctly state your issue, and its practical application?

Changing the circuit just to suit one particular load, but forgetting that you are at the same time rendering the other resistive components inconsistent in regards to properties with the original, for the solution to the problem

I do not understand what you mean by this, nor its significance in a black boxed 2 port network. If you need the internal behavior to match some hidden goal, then Thevenin won't help. Exactly what are you trying to accomplish? You have not been unambiguous about your goals.

BTW: A more significant issue with a thevenin equivalent is that the temperature of the black box can be different between the original and the equivalent. That is why I have always said "behavior at the two ports" . That is all Thevenin is concerned with: "The behavior at the two ports". If you have other requirements, then you need some other solution. Your "other solution" will probably internally use Thevenin or some close derivative. But, WHO CARES?

 

[FrankvdW]

From the point of view in an electrical way (currents and voltages) across the termial (black box with one terminal pair) you cannot imagine a any measurement to determine the content of the insite of the box. You can use non-electrical methods to detemine a Thévénin or Norton equivalent in case there is only one resistor and a source: in case of Thévénin the unloded box stay cold and the shorcircuir box becomes hot; with Noton it is just the reverse.

 

[Let'sthink]

I think the Thevnin and Norton theorems are not very fundamental ones and they represent our efforts of modelling the reality, with the help of the concept of voltage source having zero internal resistance and current source having infinite internal resistance. Actual sources provide us electric energy.

 

[meBigGuy]

I think the Thevnin and Norton theorems are not very fundamental ones and they represent our efforts of modelling the reality, with the help of the concept of voltage source having zero internal resistance and current source having infinite internal resistance. Actual sources provide us electric energy.

Not trying to be rude, but I have no idea what you are trying to say when you say "not fundamental" or " Actual sources provide us electric energy"
Any model is only as accurate as you make it. You can easily include internal source resistances as part of your model. Or not. What's your point?

 

[NascentOxygen]

Contributors must be thanked for their forebearance, but the time has come to draw the curtains over this discussion, based as it is on a flawed understanding or misapplication of Thévenin's Theorem.

Closed pending major cleanup/deletion.