Negative resistance

I read somewhere that it's possible to make negative resistance. I was wondering how we can use this. The site where i read this is:jnaudin.free.fr

 

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if by negative you mean the opposite of slowing something down, then yeah, any engine does that. i got a feeling that's not what you mean though

 

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When I say create negative resistance, it's in an electrical circuit.

 

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electric motor then?

 

no...

 

weed eater guy, take it like this: the ``thing`` is a negative resistor. Now how this resistor looks like: it's two carbon filaments forming a cross. The current goes through the carbon filaments forming a cross and somehow there's a backflow of electrons, if we place an ohmmeter after the cross thats were we can observe an about -8 ohm and more of resistance. That's how basically it works and it was discovered by Ms. Chung. You can go see the site for more info: http://jnaudin.free.fr

 

He is a little off base with what he thinks he can do with what he has.

 

You can't have negative resistance. End of story.

You calculate resistance using Ohms law, here's a nice diagram to remember;

http://www.ukradioamateur.org/foundation/gfx/dwg/vir.gif

to calculate one parameter, put your finger on the symbol, so for instance, R, for resistance, which gives you V / I.

So the only way you can get -ve R, is if you have your voltmeter hooked up the wrong way compared to your ammeter!

Negative resistance implies more electrons coming out, that going in. Fits with the 'free energy' slant on that linked web site, but that isn't going to happen. Even a battery which supplies electrons to a circuit, has a resistance.

For more detailed explanantions of current flow, voltage and resistance, go google for 'Kirchoff circuit analysis'. Kirchoff wrote down a few rules about how ciruits behave. It's all very simple, gives you a couple of simultaneous equations to play with, so ou can solve an unknown. Rules are simple. Sum of current flow into a node must equal what flows out, and the sum of potential differences always equals zero. Get's a little more complicated with LC circuits, but first things first.

 

You can have negative resistance with ohms law but it is still counted as positive as it inverts equally with the voltage +/+ -/- . I.e. only a technecality... you dont get anti resistance

 

Absolutely you can have a negative resistance. It's called a tunnel diode. In a certain bias condition the current increases with decreasing voltage. At one time they were used in most tv tuners. Probably still are. They work well for uhf/vhf oscillator and mixer applications. Basically they are amplifiers.

 

Surely this is just that the always +ve resistance becomes less for a certain range of voltages. Similarly, semiconductors can lessen in resistance when they are hot, compared to cool, and so are prone to thermal runaway when current is passed through them. It just means the graph of current against voltage isn't a straight line, or simple curve, it has asymptotes.

 

Negative resistance should probably just indicate a voltage that you did not account for - for example if you try to measure the internal resistance of a battery.(the reading is negative for a certain polarity if the voltage of the battery adds to that of the Ohm-meter).

Or it could be an abstract form of notation that few people know about.

 

Exactly. The op asked if there is such a thing as a "negative resistance", as he had read something about it. There is, ie the tunnel diode. I should perhaps add that there is nothing mysterious about such devices. They are not "overunity" and do not produce "free energy". They are simply a type of (usually) solid state devices with usefull characteristics.

 

Yeah, but if you checked the dudes link, you'd have seen that's exactly the slant of the web site.

 

My bad. Yeah, naudin is nonsense. I hate when these psuedo science types hijack real terminology and apply it to mean something else.

 

Negative resistance is perhaps incorrectly named, but it is a property of some amplifier circuits such as tunnel diodes, some transistors and vacuum tubes. Neil

 

Hello, Tc_fan,

I just want to give you a little information on Naudin before you waste too much time and effort on his ideas.

He was chased out of France a number of years ago by investors who put good money into his hare-brained schemes. He vanished for a while, reappeared in New York where he was sued (and lost) by the state Attorney General.

Then he packed up and moved to Huntsville, Alabama so that he would have a "space age" address to work from while he continued to push his con games.

He has never yet produced a working device to support ANY of his "great ideas."

You would do well to distance yourself from him and ANYTHING he suggests.

 

A device with negative resistance has current through it increase with lower voltage and decrease with higher voltage. This can be obtained in various ways, and such a device, or circuit, is basically an amplifier. The tunnel diode is one example, the now obsolete unijunction transistor is another. Of course, neither of them have negative resistance over their whole range, only part of it, so if you plot the current in the device against voltage, you will see it start by rising with voltage, then it turns and drops for a while, and finally, it rises again. In the "folded" zone, the device exhibits negative resistance.

Hans