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If there's any place that sells resistors with negative values, I'm sure they also sell perpetual-motion machines.
 

It is not a resistor, But negative resistance is possible. Some devices are also known. A tunnel diode is an example.
22_1324762696.png

Also you can refer th articles about negative resistance from wikipeadia or any research papers.
hope this gives the info you needed.
all the best
Happy Christmas.GBU
 

No, resistors do not have a negative value..
Negative resistance is only a concept...

And as said by "rkjrocks", there are some diodes that shows negative resistance properties.
Tunnel Diode, Gunn diode, Impatt, Trapatt diode are some showing negative resistance.
 

I agree with errakeshpillai .....At lest with the best to my knowledge....Negative resistence region is a charactersitcs of device like UJT.....Negative resistance is a concept.....

Good Luck
 

Hi,

What is a positive resistor?

It is a device that follows:
R = V / I
Where the direction of its current (inside of it) is from its higher potential to its lower one (their difference is V).

We can conclude that anytime a positive resistor is energized, it creates automatically a device having a negative resistor of equal value which also follows:
R = V / I
But its current direction is reversed (from lower potential instead).

The main difference of the two sides is that the positive resistor is the master while the circuit part connected to its two terminals is just its follower. So, if the resistance value of the positive resistor is 100 Ohms, the circuit connected to it will have to be also 100 Ohms though negative.

Is this philosophy or electronics? It is up to you to decide :grin:

Kerim
 

Hello Kerim!

I'm having a hard time following your way of thinking. Negative resistance means current is increased when resistance is rising and vice versa. Minus symbol (-) is used to declare reversed current direction, but the absolute value of the current will still be increased when the resistance value drops.

Alexandros
 
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    KerimF

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Negative resistance is a reality proved, established and used since long. Tetrode valves show negative resistance region which has been exploited usefully for long time beofore the latest technology took over.
When you call it concept, concept can be real too. What is concept and reality.
A Raoof Khan
 

There is one important aspect that I have missed in all the contributions up to now:
When we speak about resistances - in particular with V-I characteristics similar to the graph as shown in posting#5 - it is absolutely necessary to distinguish between static (dc) resistance and dynamic (differential) resistance. Otherwise no logical and consistent explanation is possible.
By the way: Negative resistance is neither a "concept" nor a pure mathematical fiction. It is a real device resp. circuit that can be realized.
 
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KerimF said:
Hi,

What is a positive resistor?

It is a device that follows:
R = V / I
Where the direction of its current (inside of it) is from its higher potential to its lower one (their difference is V).

We can conclude that anytime a positive resistor is energized, it creates automatically a device having a negative resistor of equal value which also follows:
R = V / I
But its current direction is reversed (from lower potential instead).

The main difference of the two sides is that the positive resistor is the master while the circuit part connected to its two terminals is just its follower. So, if the resistance value of the positive resistor is 100 Ohms, the circuit connected to it will have to be also 100 Ohms though negative.

Is this philosophy or electronics? It is up to you to decide :grin:

Kerim
Click to expand...


I too having another thought Kerim, The transfer of electrons from a lower potential to a higher potential is possible by supplying energy to the circuit. I think the negative resistance concept is when voltage is increasing, the current is decreasing. or when voltage decreasing the current is increasing.. I think revesing the direction of current has nothing to do with negative resistance,,,,,

it is like LvW says....... It is possible to have negative resistance, like the incremental negative resistance of Tunnel diode, or true negative resistance circuit like negative impedance converter
Have a look in following page.......Negative impedance converter - Wikipedia, the free encyclopedia
 
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There is a component that let its current decreasing when its voltage increases though you won't call it having a negative resistance. Could you guess it? :twisted:
 
Addition of a resistance will decrease the value of current that is flowing in the circuit. But anyhow its not going to decrease it to "zero or less than that" (Open circuit as an exception). Now with the negative resistance phenomena, the current is flowing in the direction reverse to the expected direction, of course the reason being some other phenomena like tunneling, Gunn effect or so. So what is this effect called...????
This is termed as negative resistance.
 

KerimF said:
There is a component that let its current decreasing when its voltage increases though you won't call it having a negative resistance. Could you guess it? :twisted:
Click to expand...

Hi KarimF,
are you talking about transformers????:!:

:roll:
wait a minute,.....................8-O
now that i think about it..............then I have another doubt to ask to you?

is it because of the opposition of negative directed current (reverse directed), the value of the +ve directed current is decreasing even if the voltage is increasing???
 

As mentioned already several years ago: A graph can reveal more details than 1000 words.
Thus: It is surprising that nobody uses the graph as given in posting #5 to formulate his position.

It's so simple: The graph shows the V-I characteristic of a NON-LINEAR device.
As can be seen, there is a range where the DC current falls with a rising dc voltage.
This is equivalent to a negative slope of the curve. Thus, the ratio delta-V/delta-I is negative.
This is equivalent to a negative differential (dynamic) resistance.

On the other hand, there are active circuits (NIC) that are able to realize LINEAR V-I characteristics identical to negative resistances.
In this case, there is no difference between static and dynamic behaviour. The magnitude of the current is proportional to the voltage magnitude - however the DIRECTION of the current is inverse if compared with a classical (positive power consuming) resistor.
 
KerimF said:
There is a component that let its current decreasing when its voltage increases though you won't call it having a negative resistance. Could you guess it? :twisted:
Click to expand...

This component can have the negative V-I slope once in its life... It is the fuse :-D
 
KerimF said:
It is the fuse :-D
Click to expand...

well in the case of fuse, as the voltage increases the current too increases like normal, but when ti exceeds the limit as you says,
This component can have the negative V-I slope once in its life...
Click to expand...
blown out.....................
great KerimF
 

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