Talk:Circuit Idea/Deborah Chung's "Apparent Negative Resistance" - Wikibooks, open books for an open world

In this discussion I will unveil the mystery behind the Chung's experiment - the greatest misconception in the area of the negative resistance phenomena. Circuit-fantasist (talk) 16:11, 10 January 2009 (UTC)Reply

A week ago, I received an email from Robert Michaels; he said he was impressed by my discussions about the negative resistance phenomenon. He was interested in using thermal effects in electronic devices for obtaining a negative resistance (interesting, so I hope he will join our discussion). But here I would like to say that he provoked my interest in Chung's "apparent negative resistance" as he was speaking about it with respect.

I read closely the section and the old discussion about this scientific sensation where I found interesting speculations (e.g., the "bridge" and "transresistance" viewpoints). For my great surprise, I did not find any negative resistanse in this arrangement - neither absolute nor differential! I did not find even the more ordinary dynamic resistance in this arrangement; imagine there was only an odd carbon-fiber network having an ordinary, bare, "19th century" ohmic resistance! I had the feeling I was seeing some of Edison's carbon microphone experiments...

Finally, I realized this exotic carbon fiber arrangement acts as some kind of bridge circuit formed by two kinds of resistances - steady carbon fiber resistances R and varying contact resistances Rc (you may find also the same "bridge viewpoint" in the old discussion). In some way (for now unrecognized), it turned out they were connected in the opposite bridge legs. By the way, a long time ago I was impressed by this remarkable feature of the bridge circuit - to reverse the output voltage. It can do that because the output voltage is a differential quantity. It is "flying"; it is the difference between the two grounded voltages - V_R and V_Rc. Depending on the proportion between R and Rc, this difference may be zero (R = Rc), positive (R > Rc) or negative (R < Rc). And, if we assume the current I_IN is the input quantity and the voltage V_OUT is the output quantity, we may think of this device as a zero, a positive or... a "negative" transresistance converter:) But this is not a negative resistance; this is not even a resistance; it is the more abstract transresistance (you may find also the same "transresistance viewpoint" in the old discussion)! Circuit-fantasist (talk) 16:11, 10 January 2009 (UTC)Reply

Once revealed the general idea behind this experiment (to be more precise, the absence of any idea) I loosed any interest in thinking about it. I knew what the carbon fiber network actually did but yet.. it was a great challenge to understand how the carbon fiber tangle did this "magic". And I began thinking again... Circuit-fantasist (talk) 16:11, 10 January 2009 (UTC)Reply

Well, let's look at the left picture below and begin thinking together. The two laminae are connected to each other by great number of contact resistances Rc; you may think of the central cross area as a kind of cube. The current flows from the top lamina that is positive to the bottom lamina that is negative. So, the upper point B is positive and the lower point D is negative; the output voltage V_OUT has a positive polarity as it is shown on the picture. The "resistance" is positive: R = V_OUT/I_IN > 0.

Now, let's look at the right picture below and continue thinking together. Now, a big pressure is applied; so, the two laminae are connected to each other by great number of zero contact resistances. In this case, the central cross area is a flat grid. The current goes into the left side of the grid, turns to the bottom and goes out from the bottom side of the grid. In this situation, the point D stays closer to the positive terminal of the input voltage source and the point B stays closer to the negative terminal. So, the point D is more positive than the point D and the output voltage V_OUT has a negative polarity as shown on the right picture. As a result, like Professor Chung, we might draw a wrong conclusion that the "resistance" is "negative": R = -V_OUT/I_IN < 0 and to begin making a stir.

Finally, we may suppose there is some middle pressure between the extreme limits when the output voltage V_OUT is zero. The "resistance" is zero as well: R = V_OUT/I_IN = 0.

Then, what has Professor Deborah Chung actually observed? What has she done? Let's try to answer...

It is clear she have made some kind of exotic bridge circuit depending on applied pressure. Indeed, this carbon fiber arrangement can serve as an odd voltage-to-voltage converter, a current-to-voltage converter or as a (poor) pressure-to-voltage converter (a pressure sensor). But IMO, there are no any benefits of using it; contrary, there are many losses... Only see in Google how many people are involved in this useless discussion and how much efforts, time and money are wasted... It is a pity to see how people relying more on "reputable" sources than on their own human common sense are misleaded!

There is not any connection between this experiment and the negative resistance phenomenon.

There is not any apparent, absolute, differential or even dynamic resistance in this arrangement; there is only ordinary, bare, "19th century" ohmic resistance.

Chung's carbon fiber network behaves actually as an odd bridge circuit depending on the applied pressure (like the ordinary tensometric bridge circuit).

It seems Chung's experiment is the greatest misconception in the area of the negative resistance phenomena.

Circuit-fantasist (talk) 16:11, 10 January 2009 (UTC)Reply

I have noted with a satisfaction that finally the confusing Wikipedia page about the wrong Chung's assertions is deleted. Circuit-fantasist (discuss • contribs) 21:49, 13 May 2012 (UTC)Reply