Do you think an LED is a resistor?

[xrunner]

I might start a new thread because this is so interesting -

Do you think a Vise-Grip is a hammer?

After all, I can hammer a nail with a vise-grip. If I give you two pieces of wood with driven nails - can you tell which one had the nails driven with a hammer and which one has nails driven with a vise-grip?

So I want to know if a vise-grip is in fact just another form of a hammer. Prove me wrong.

[PlainName]

Has the poll answers text been changed?

[MK14]

Has the poll answers text been changed?

No, I don't think so.

[armandine2]

I might start a new thread because this is so interesting -

Do you think a Vise-Grip is a hammer?

After all, I can hammer a nail with a vise-grip. If I give you two pieces of wood with driven nails - can you tell which one had the nails driven with a hammer and which one has nails driven with a vise-grip?

So I want to know if a vise-grip is in fact just another form of a hammer. Prove me wrong.

I was also thinking on mechanical lines 

... so if the electrical terms Resistance, Inductance and Capacitance have their mechanical equivalents what is the OPs mechanical device analogous to the LED? 

[Sredni]

non linear system has linear approximation around a small operating point....

STOP THE PRESSES!

... oh wait, that's the underlying principle of how spice AC analysis works.

Small signal analysis has nothing to do with what we are discussing here.
The resistance I talk about is the static resistance, not the dynamic or incremental resistance of small signal analysis.

Try again.

That was your long winded and dithering proof:

So, we are now seeing the diode as a voltage dependent resistor. Let's see... what is the resistance 400mV? Let's zoom in:

[MASSIVE IMAGE]

I'd say it's about 23.2 kohm.
Let's see what is the resistance at, I don't know, 660 mV (about 5mA of diode current). We can compute it by hand of course, but on the graph we see it is 132 ohm.

[MASSIVE IMAGE]

Now, let's see if we can make something with these values...
[snipping conversational fluff]
Ok, exact same results, if we neglect a bit of rounding error in reading and setting the values.
Now, take your black boxes out of the fridge. Put the diodes D1 and D2, and the resistors R1 and R2 inside a black box each. Shuffle them around. And tell me: without looking inside the black boxes and without resorting to second order effects (like temperature dependence, or changing the other circuital parameters to change the operating points) can you tell me which are the diodes and which are the resistors, by simply measuring voltages, currents and powers?

So to try and claim you're not relying on the well known small signal AC parameters is plainly incorrect.

If you dont like relying on small signal characteristics, perhaps "try again" with your explanation/justification.

Again, small signal analysis has nothing to do with anything I have written in that post.
Nothing.
I zoomed in on the V-R characteristic to find an accurate value of the static resistance. Not the dynamic, or incremental, or small signal resistance.
Then I used the static resistance at a chosen voltage or current to choose the limiting resistor that would have set the chosen operating point.
Then I showed that using a resistor with the correct static resistance value would give the same variables in the circuit..
If you want to waste a bit of time you can create in LTspice a voltage controlled resistor that has the same R=R(V) dependence of a 1N4148. You will then see that it will behave (secondary effects apart) as a diode, confirming that it's the variable resistance. that gives a diode its behavior.

Go ahead and try.

[MK14]

I am still NOT convinced.  I don't think an LED and a resistor are the same.

Apart from anything else, an LED is normally used as a light source or indicator.  Functions which a normal, non-overloaded resistor can't do.  At least in the visible spectrum.

[Sredni]

I might start a new thread because this is so interesting -

Do you think a Vise-Grip is a hammer?

After all, I can hammer a nail with a vise-grip. If I give you two pieces of wood with driven nails - can you tell which one had the nails driven with a hammer and which one has nails driven with a vise-grip?

So I want to know if a vise-grip is in fact just another form of a hammer. Prove me wrong.

I was also thinking on mechanical lines 

... so if the electrical terms Resistance, Inductance and Capacitance have their mechanical equivalents what is the OPs mechanical device analogous to the LED? 

Not sure you can find one with the exact same characteristic, it should have to be a dashpot that opposes diminishing resistance with increasing force.
If you consider an ideal diode, well a valve opposes infinite resistance to fluidmotion due to negative flow, and zero resistance to theotion with positive flow.
An electrician's zip tie allows you to slide freely in one direction and blocks the motion in the opposite direction, so it has a friction coefficient that depends on the sign of the force you apply to one end. You can consider it a force dependent friction device.

But maybe there is not an hydraulic or a translational or rotational mechanical analog of an exponential diode.
What is the mechanical analog of a Josephson junction?

[IanB]

what is the OPs mechanical device analogous to the LED?

This is interesting actually. The mechanical equivalent of an electrical diode is a non-return valve in hydraulics. What makes it interesting is that a non-return valve requires fluid flow to operate it (to make it open and close). For example if the valve is open and you want it to close, it requires a small amount of backflow to make it shut off--it is not instantaneous. There is a similar behavior in electrical diodes, where they do not operate until current flows through them. The amount of charge required to switch the state leads to the difference between fast signal diodes and high power diodes that switch more slowly.

[Sredni]

I am still NOT convinced.  I don't think an LED and a resistor are the same.

Apart from anything else, an LED is normally used as a light source or indicator.  Functions which a normal, non-overloaded resistor can't do.  At least in the visible spectrum.

I specified "from the point of view of circuit theory". From the point of view of the circuit it does not matter that the power extracted from the circuit by the diode resistance goes all in heat (IR light), visible light, UV, or chemical energy.

And saying that a LED or a diode is a resistor does not mean they have to be the same thing as another member of the set "resistors". It means that a LED or a diode is one kind of, is a type of, is one member of the wide set resistors.
The set "Resistor" is a set that encompasses linear resistors and nonlinear resistors, and nonlinear resistors include - among others - incandescent lamps, signal diodes, zener diodes, wieners and so on.

"This is Helen, she's a woman"
"Don't be silly! Kate is a woman, and Helen is clearly not Kate! She's not even blonde!!!"
"I assure you, she's a woman, just a different hairtype woman."
"Are you trolling me? The people in Stockholm are laughing at you right now. Look at Inga, that's a woman., and guess what? She's blonde too".



 

[PlainName]

For example if the valve is open and you want it to close, it requires a small amount of backflow to make it shut off

Until springs are invented.

Wouldn't that be a closer analog to a diode? The small amount of pressure required to overcome the spring would be similar to Vf of the diode.

[Sredni]

Resistor < Linear resistor U Nonlinear resistor
Nonlinear resistor < incandescent lamps U diodes U ...

So, you can still call it a diode, recognize that it is a nonlinear resistor and, as such, that it belongs to the more general set of resistors.

Does this make any sense to you?

It does not make sense.

All resistors exhibit electrical resistance.
All of those semiconductor devices indeed also exhibit electrical resistance.
However not all devices that exhibit electrical resistance are resistors as they are not components purposely designed to implement a well defined resistance.

Does not matter what you understand as "resistor", the vast majority of forum members you are talking to on here understand it as a device specifically designed to implement a well defined amount of resistance. You don't have the authority to redefine established industry words used by others.

What you are trying to say is that a diode exhibits the effect of "electrical resistance" or "resistivity".

This effect is not particularly special and just describes that the device can consume electrical power and turn it into something else,

The point I make is that this is ALL a diode does.
Huge resistance when reverse biased, small resistance when forward biased. This is not a side effect. It is what it does (if we neglect secondary effects due to parasitics in real devices).
It does not store energy in the electric field.
It does not store energy in the magnetic field.
It does not do whatever sorcery a memristor does.
It just oppose a resistance that takes power out of the circuit.

Yes we all agree on here that at some fixed DC operating point a diode acts like resistance.

The point is that a diode is nothing special at doing this. The laws of physics force all power consuming components to look like resistors in steady state DC. This means that at a fixed DC operating point even a memristor is actually just electrical resistance, much like a diode acts as purely electrical resistance at that DC state.

Like what else do you expect an component to do at DC? It can either act as a power source (like a voltage or current source) or it can resist the flow of current hence resistance. There is nothing else for a component to do at DC.

There is so much to unpack here but let's consider only the last part.
A capacitor at DC can hold a voltage without passing current; try to do that with a resistor.
An inductor at DC can hold a current without a voltage (if ideal, and a small voltage due to small resistive losses if real). Try to do that with a resistor.
You can use these properties to create memory cells. Try to do that with resistors alone.
I am not well versed in memristors to give an elementary setting that shows their fundamental difference from resistors, but I am pretty confident  you got that part wrong, as well.

Have you looked up the Science Direct link I gave above? I am not redefining industry standard terms: diodes have been considered to be nonlinear resistors for decades. You just wasn't aware of it.

[Sredni]

Second condition is sometimes relaxed - e.g. variable resistors, thermistors, light-dependent resistors - but they are never called just "resistors", but with resistor only as part of the full name.

I don't suggest renaming something which already has another name, though, such as "light-emitting diode", as "non-linear light emitting resistor", even if you technically could. Maybe if it was originally named that way, we would be fine with the name. Then we would likely see Sredni creating a thread about how this non-linear resistor should be actually called a "diode".

This is not about the naming per se, it is about the fundamental nature of a diode from the point of view of the circuit. All it does (neglecting secondary effects) is offering a resistance.

I am not saying that since Helen is a woman, she should be addressed as "woman". You can still call her Helen, but that does not mean she ceases to be a woman. And the fact that Helen and Kate are different individuals does not implies that one of them is not a woman.

Seriously, all this seems to point to a broader problem than I had thought. People here seem to have a problem in understanding set inclusion. Could it be it has been removed from elementary school curricula in the last decades?

[Kim Christensen]

This is not about the naming per se, it is about the fundamental nature of a diode from the point of view of the circuit. All it does (neglecting secondary effects) is offering a resistance.

Now you say it... yet your poll asked this:

Is an LED a resistor?
No. It has a different name, so it is not a resistor
Yes. It is a resistor, just not an ordinary one

You don't seem to realize that no one has an issue with a LED, or any other device, having resistive properties. We have an issue with you calling it a type of resistor.

resistance vs resistor 

[IanB]

You don't seem to realize that no one has an issue with a LED, or any other device, having resistive properties.

Of course Sredni realizes that. But if they acknowledged it, it would not serve the purpose of trolling the forum with a seven page thread.

[bdunham7]

People here seem to have a problem in understanding set inclusion.

The problem isn't most of us not understanding what LEDs are nor how basic set theory works.  The problem seems to be you trying to interweave a poorly constructed semantic argument with a particular type of circuit theory.

I'll leave the circuit theory to others such as switchabl who seems to be more familiar with nonlinear network theory than I am.  If we're going to have a discussion about memristors and the theory that posits them, that should be another thread.  It actually might be an interesting topic, but not an uncontroversial one from what I've read.  If anyone has a copy of or link to Chua's original paper, I'd like to see it as I haven't found it outside of a paywall.

Your semantic argument here seems to be that if you describe something using an adjective and a noun, then what you are describing is automatically a member or subset of the set of things described by the noun alone.  This is quite foolish and not how the English language works.  It is fairly common to describe things using an adjective/noun combination that is inherently oxymoronic.  Non-dairy milk, vegan hamburger, etc.  Whether these specific things are to be included in the larger set depends on the precise nature of what you are describing and the definition of the set, not just word combinations.

If you have a silver Rolex, a gold Rolex and an old Rolex, they are all members of the set Rolex.  However, does that mean that a fake Rolex is a Rolex?

Is a Gunn diode a diode?  Define diode first, then look up what a Gunn diode is and decide. 

The typical, ordinary definition of a resistor is a device that obeys Ohms law, IOW has a nominally linear V/I plot that goes through 0,0.  Thus the term "non-linear resistor" is oxymoronic using this definition and we would not include it in the set.  If you redefine the term 'resistor' to mean something other than what I've stated, then perhaps your definition can include LEDs and so forth.  As many have told you already, most of us would find this inclusion to be unhelpful.  This is not to due to stupidity or some great educational lacuna so please get over yourself and your pseudo-iconoclast act.

[Sredni]

This is not about the naming per se, it is about the fundamental nature of a diode from the point of view of the circuit. All it does (neglecting secondary effects) is offering a resistance.

Now you say it... yet your poll asked this:

Is an LED a resistor?
No. It has a different name, so it is not a resistor
Yes. It is a resistor, just not an ordinary one

You don't seem to realize that no one has an issue with a LED, or any other device, having resistive properties. We have an issue with you calling it a type of resistor.

resistance vs resistor 

Yes, because the mental block a lot of people have in recognizing that a diode (an LED) is a resistor seems rooted in the fact that it has a different name.
As if giving it a specific name could change its fundamental nature.

What a diode does is offering a resistance that changes with voltage or current. You can create a voltage dependent resistor in Spice with the same V-R characteristic of a silicon diode and it will behave the same at every current and voltage.

Have you looked up the Science direct link I gave above? It mentions multiple textbooks using the term nonlinear resistor without even batting an eye, and also acknowledging that a diode is a nonlinear resistor. Do you think they are trolling?

[BU508A]

Do you think they are trolling?

Perhaps not, but I think, you are the troll here. At least in this thread.

[Sredni]

Here

https://www.vishay.com/docs/29235/elecsimtoolkitvishaynlr.pdf

Go tell Vishay they are using an 'oxymoronic' terminology.
After all what could they know about electronic components?

[magic]

Yes, because the mental block a lot of people have in recognizing that a diode (an LED) is a resistor seems rooted in the fact that it has a different name.
As if giving it a specific name could change its fundamental nature.

Have you considered the possibility that the diode was given a different name after some very smart experts realized that it really is a fundamentally different thing than a resistor?
 

[bdunham7]

Go tell Vishay they are using an 'oxymoronic' terminology.
After all what could they know about electronic components?

Calling a term oxymoronic doesn't imply that it is inherently erroneous, merely that there is a tension or conflict between two parts of the term.  I have no problem with the term "nonlinear resistor" and neither does anyone else.  You're tilting at imaginary windmills here.  Oxymoronic terminology is common when seeking to distinguish something from a set while also claiming some similarity, thus my example of non-dairy milk.  I have no issue with the term 'almond milk' as it readily describes the product, but if I ordered a gallon of milk without further specification, I wouldn't be happy if they delivered almond milk. 

Perhaps this brief tutorial will help:

https://www.skillshare.com/en/blog/the-oxymoron-a-terribly-helpful-literary-device/

[Berni]

There is so much to unpack here but let's consider only the last part.
A capacitor at DC can hold a voltage without passing current; try to do that with a resistor.
An inductor at DC can hold a current without a voltage (if ideal, and a small voltage due to small resistive losses if real). Try to do that with a resistor.
You can use these properties to create memory cells. Try to do that with resistors alone.
I am not well versed in memristors to give an elementary setting that shows their fundamental difference from resistors, but I am pretty confident  you got that part wrong, as well.

Have you looked up the Science Direct link I gave above? I am not redefining industry standard terms: diodes have been considered to be nonlinear resistors for decades. You just wasn't aware of it.

Yes and we have names for a resistive device that is designed to be very non linear, the industry standard term for that is a varistor instead of resistor.

If you just generalise all these things are being resistors, then you could also generalize all diodes as diodes (even tho they act very differently), then it falls apart even more as some TVS diodes exhibit a memrisor like behavior (they clamp down and stay clamped until you reduce the current, hence have memory of previous current). But that's besides the point. Diodes exhibiting electrical resistance is nothing special or ground breaking. Everyone in this thread knows about it.

The only problem is that you are throwing around the term resistor and resistance as being the same thing. They are not. The resistor is the industry standard term for a device that is designed to create the effect of resistance in a well defined manner. While electrical resistance is a physics phenomenon where something opposes the flow of current in a electrical circuit.

What is the point you are trying to make with this thread? That a diode has electrical resistance? Or that everything that exhibits electrical resistance should be called a resistor?

[Sredni]

Have you looked up the Science Direct link I gave above? I am not redefining industry standard terms: diodes have been considered to be nonlinear resistors for decades. You just wasn't aware of it.

Yes and we have names for a resistive device that is designed to be very non linear, the industry standard term for that is a varistor instead of resistor.

Ok, let's start from here. In a previous post you wrote

...a resistor where its resistance is strongly affected by the voltage across it is called a varistor or "voltage dependent resistor". So if you are to draw similarities, you can say a diode is a form of asymmetrical varistor.

So, is a varistor a resistor? You wrote right there: "a resistor where [...] is called a varistor or voltage depent resistor. I'd say that you just said a varistor is a special type of resistor.
And since you also write that a diode is a form of asymmetric varistor... What does that make a diode if not a special kind of resistor?

Do you see the cognitive dissonance, now?

The only problem is that you are throwing around the term resistor and resistance as being the same thing.

No. Resistance is the property. Resistor is the component exhibiting the resistive property. If resistance is constant, the resistor is linear; if it is not, it is nonlinear.

They are not. The resistor is the industry standard term for a device that is designed to create the effect of resistance in a well defined manner. While electrical resistance is a physics phenomenon where something opposes the flow of current in a electrical circuit.

What is the point you are trying to make with this thread? That a diode has electrical resistance? Or that everything that exhibits electrical resistance should be called a resistor?

I am trying to uncover the roots of this cognitive dissonance. First you say that varistors are resistors that... And then you say no, they are not resistors, because resistors are only linear.

Go on that Vishay page that shows how to simulate nonlinear resistors (a term that up to a few messages ago you people thought I had invented, LOL) and simulated your resistor with an exponential characteristic. There you have your diode. It is a nonlinear resistor.

[Zero999]

Perhaps a thyristor is another type of resistor, since it has ristor in it?

Nonsense. A resistive load will always result in unity power factor when connected to an AC source. A diode will not give unity power factor, when connected to an AC source, therefore it is not a resistor. End of discussion.

[Kim Christensen]

Here
https://www.vishay.com/docs/29235/elecsimtoolkitvishaynlr.pdf
Go tell Vishay they are using an 'oxymoronic' terminology.
After all what could they know about electronic components?

Hit CTRL-F and search for the word "diode" in that document. There are only 3 occurrences of the word diode. In none of those sentences do they claim that a diode is a resistor. 

[Sredni]

Here
https://www.vishay.com/docs/29235/elecsimtoolkitvishaynlr.pdf
Go tell Vishay they are using an 'oxymoronic' terminology.
After all what could they know about electronic components?

Hit CTRL-F and search for the word "diode" in that document. There are only 3 occurrences of the word diode. In none of those sentences do they claim that a diode is a resistor. 

Well, up to a few posts ago, "nonlinear resistor" was an oxymoron, so it's progress.

Try this. Go here: https://automobiles.honda.com/ (or any other car manufacturer) and try to find a Formula1 race car for sale.
If you can't find it then Formula 1 race cars are not cars.

Helen is a woman, even if you don't find it in the list of women whose name starts with K, like Kate.