Do you think an LED is a resistor?

[PlainName]

It is what it makes it a diode

That's what you  keep getting told. A diode has non-linear resistance. A resistor has linear resistance.

[Sredni]

It is what it makes it a diode

That's what you  keep getting told. A diode has non-linear resistance. A resistor has linear resistance.

So you agree that a diode is a nonlinear resistor.

But you don't think that nonlinear resistors are... resistors. Correct?

[Zero999]

Non-linear resistors are not resistors. They are something else: diodes, DIACs, varistors etc. but not resistors. End of discussion.

[tom66]

This whole thread is a meaningless semantic argument, ultimately why does it matter if you want to go against the grain of most engineering and call a diode a resistor with non-linear properties then go ahead... but does it have any use in the real world?  No, it does not.  You can define a diode by a Vf and a few other basic parameters and get a useful result that is close to real world behaviour, but you cannot usefully define a diode by a resistance as the apparent "resistance" varies significantly across the V/I curve.  End of argument.  I really can't believe this has gone on for 9 pages.

[Sredni]

This whole thread is a meaningless semantic argument, ultimately why does it matter if you want to go against the grain of most engineering and call a diode a resistor with non-linear properties then go ahead... but does it have any use in the real world?  No, it does not.  You can define a diode by a Vf and a few other basic parameters and get a useful result that is close to real world behaviour, but you cannot usefully define a diode by a resistance as the apparent "resistance" varies significantly across the V/I curve.  End of argument.  I really can't believe this has gone on for 9 pages.

"Most engineering"? Are you sure that 'most engineering' do not realize the diode is a nonlinear resistor? I mean you can bring a load of vocational school books that do not need to go any further than a superficial hands-on description of the devices, but when it comes to serious engineering books, and even more so circuit theory books, and even more so nonlinear circuits theory books, it is glaring evident that a diode is a nonlinear resistor.

Even mainstream references, like "The Electrical Engineering Handbook" leave no room to ambiguities:

Nonlinear resistors commonly used in electronic circuits are diodes: exponential, zener, and tunnel (Esaki) diodes.

Maybe you can call Elsevier, or Simon Fraser university and tell the author of that chapter that they are going against the grain of 'most engineering'.

It took 9 pages because the objection shifted from "if it's a diode its not a resistor, duh", to "there is no such thing as a nonlinear resistor", to "nonlinear resistors exists but they can only be varistors, lamps, but not diodes", to "diodes are nonlinear resistors but nonlinear resistors are not resistors".

Edit: grammar

[MK14]

Bold and font size change, done by me.

I am curious. How many of you people think an LED is a resistor? I should add: from the point of view of circuit theory, not from that of technology and underlying physics.

(This question originates from a question in another forum, where polls are not possible).

You specifically said "resistor", in the poll.

So you can't start changing the "resistor" to other things, such as "non-linear" resistors, later in the thread.

Because it makes the poll (and possibly the thread), relatively meaningless.

[Sredni]

A nonlinear RESISTOR is a RESISTOR.

nonlinear here is an adjective that specifies a particular property of a subset of the general set of resistors.

A bald man is a man.
A one-legged man is still a man, even if in all medicine books the body of a man is shown with two legs.

A nonlinear inductor is still an inductor.
The inductors used in Single Ended Primary Inductor Converters are usually nonlinear but they are called inductors nonetheless. Have you ever read "the nonlinear coil two-port element's current is..." In the description of a switching circuit? No, everybody says "the inductor's current..."

Sheesh...

[Gyro]

This is getting nobody anywhere...

In the real world, semiconductors, including diodes (of all flavors) have datasheets. These specify the typical and worst case voltage / current characteristics under defined conditions. People find these USEFUL in designing them into circuits and products in the real world. Your dogmatic semantic argument that they are all resistors is NOT USEFUL in the real world. See the distinction?

Your dinner tonight will have electrical resistance, which will be determined by its composition temperature etc. as will the plate it is sitting on, the table they are sitting on, the chair you are sitting on (and the arse you're sitting on it with). Will you sit there making semantic arguments that they should all be defined as resistors until it gets cold (or in your case possibly moldy), or in the real world, will you just eat it?

[MK14]

A nonlinear RESISTOR is a RESISTOR.

nonlinear here is an adjective that specifies a particular property of a subset of the general set of resistors.

If someone in an opening forum post, says "Resistor".  That should mean a component, which obeys (without any trickery or messing around) Ohms Law.  So it can't be a non-linear thing.

If it is (or could be something) which doesn't obey Ohms Law and/or a weird type of resistor.  Then that should be clearly stated in the opening post/poll.

Otherwise, you are moving into the realms of (similar to), trick questions.

When making polls, it is very important that the question(s) and propositions etc.  Are very unambiguous, to a very wide audience.  Otherwise the poll results and possibly the thread, may just descend into massive arguments.

[bdunham7]

A bald man is a man.
A one-legged man is still a man, even if in all medicine books the body of a man is shown with two legs.

How about a fictional man?  Or a robotic man?  An AI man?  A virtual man? 

As I clearly explained earlier--and you appear to have used the concepts I explained and twisted them around to your own ends--something described by an adjective plus a noun does not necessarily belong to the set of things described by the noun alone.  So it all boils down to how you choose to define resistor.  And stop with the bleating that these aren't YOUR definitions but rather those of some famous people we're bound to respect--you don't have to invent the descriptions, they become "yours" if you choose to adopt them.  My definition of convenience is that the term 'resistor' used alone with no prefix means a fixed, nominally linear resistor.  I didn't invent that.

Wikipedia has an interesting statement--"The electrical function of a resistor is specified by its resistance".  I like that.  Is an LED's function specified by a resistance value?  There's an opening for you in that statement, perhaps you'll get another 9 pages out of it.

[PlainName]

It is what it makes it a diode

That's what you  keep getting told. A diode has non-linear resistance. A resistor has linear resistance.

So you agree that a diode is a nonlinear resistor.

But you don't think that nonlinear resistors are... resistors. Correct?

I think you need to take a course in reading comprehension. Ask an optician why you keep seeing 'resistor' where it really says 'resistance'.

[BU508A]

Because I am discussing the FUNDAMENTAL nature of the diode.

This is the fundamental behaviour of a diode. Doesn't really look like a resistor.

[Sredni]

That's a piecewise linear resistor: infinite resistance under threshold voltage, zero resistance above.
Really, this is basic circuit theory.

And no, to answer other objections I use resistor and resistance with care: resistance is the property, resistor is the circuital element.
A linear resistor (generally called "resistor" without adjective) has constant resistance. A nonlinear resistor has voltage or current dependent resistance.

And yes, form the point of view of the circuit all a (linear or nonlinear) resistor does is opposing a resistance and dissipate power. Dissipate means it leaves the circuit. It does not matter in what form: heat, light, chemical energy...
I have simulated LEDs in LTSpice and never saw light coming out of the screen :-)

[AVGresponding]

Every time I glance at this thread, I can feel IQ points evaporating

[bd139]

Is a non-linear resistor, like a thermistor non-linear in at least a small signal model at a set temperature? No it's linear because "R" is constant under those conditions and not dependent on I or V.

The definition of a non-linear resistor is even broken according to the arguments here.

So you can't even reason about the thought framework the question is posed in because it's so poorly defined.

Therefore I posit that it doesn't matter if anyone thinks an LED is a resistor or not, the original poster is a troll trying to be clever, thus is a dickhead and a fuckwit and this thread should be locked.

[edavid]

The original poster is a ... fuckwit and this thread should be locked.

Can we get a button for that?  It's a pain having to type it every time 

[Bud]

Cant believe this garbage thread is still continuing 

[Sredni]

Is a non-linear resistor, like a thermistor non-linear in at least a small signal model at a set temperature? No it's linear because "R" is constant under those conditions and not dependent on I or V.

The definition of a non-linear resistor is even broken according to the arguments here.

You don't understand the difference between small signal and large signal analysis.
You want to lock the thread because of that?
Have you seen the list if references I have given? Are they all troll (and the other names you called me)?

I assure that they, at least, understand what small signal analysis is about.

Again, I do not respond to provocations. If you don't like how Vishay classifies their components, or how experts on circuit theory call the fundamental circuital elements, just don't read this thread.

[fourfathom]

The original poster is a ... fuckwit and this thread should be locked.

Can we get a button for that?  It's a pain having to type it every time 

"JFW" works for me (Just F****** Wow!)

Resistor != Resistance

But it's fun to watch someone being so painfully obtuse.  Also kind of sad.

[bd139]

...or how experts on circuit theory call the fundamental circuital elements, just don't read this thread...

Ok in that case, give me a proof in any suitable domain, other than laplace for obvious reasons but I'm sure you know why that is[1], showing any equivalence between any transfer or large/small signal model of a resistor and an LED where I or V depend on R and not an external factor and vice-versa.

I expect you to explain this mathematically.

[1] feel free to explain for those who don't.

[Sredni]

A bald man is a man.
A one-legged man is still a man, even if in all medicine books the body of a man is shown with two legs.

How about a fictional man?  Or a robotic man?  An AI man?  A virtual man? 

Seriously?
Is a non-car a car?
Is a carrot a car?

We are at this point?
If you had read any of the circuit theory or general engineering books I have given you would know that in order to be part of the set --- let's call "all resistor" the elements need to share a common trait. Like when in that video for kids you have all vegetables in one set and all fruits in another set (and don't bring out the tomato!).

So, what is the common trait shared by the elements of the set "all resistors"? It's that they are fully characterized by a relationship between voltage and current. Only between V and I. Not q and V (those are capacitors) and not phi and I (those are inductors).

So, "all resistors" have a characteristic that is implicitly defined by  f(v, I)=0, that is a curve in the vi plane.

Now, among all these resistors, some have a curve that is a straight line, that is a v + b I = 0, which you can rewrite as v = R I. This is the subset "linear resistors" of the set "all resistors". It is a very important set because it has all the easy to understand properties of linear functions, including superposition. That is why we strive to make our components the more linear possible (yes, the five striped thingies called "resistors" you can buy are actually nonlinear and can only be considered linear within specified limits). Since they are so easy to understand, we teach about them in high school and we simply call them "resistors" not to overload feeble minds with unnecessary complications
 
But the set "(linear) resistors" is not the entire set "all resistors". We are left with all those components that are described by a VI characteristic that is NOT linear, like diodes, scrs, mov, incandescent lamps, neon bulbs... These form the huge subset "nonlinear resistors" of the larger set "all resistors". So, they are resistors with f(v,I) nonlinear.

And no, a carrot is not a car.

[bd139]

You sound like a programmer. Only programmers fuck up taxonomies this badly.

[Simon]

As predicted you started a stupid poll to piss everyone off by changing the question. Why don't you go back to those other forums where got your stupid little smartarse question. Come back when you have grown up!

[EEVblog]

Is this one of those trick questions where you pull a small-signal model out of your hat when everyone's distracted or explain later that when you said "resistor" you didn't actually mean resistor?

No, no trick question at all.
I can even show my hand: it is a resistor, a nonlinear resistor to be precise. Why? because its state is determined by the present values of voltage and current (and not their derivatives and integrals like capacitors, inductors, and memristors).

But a lot of people have trouble in recognizing that.

A diode is a resistor in the same way an incandescent lamp is a resistor. Both are nonlinear and both have exponential V-I characteristics. And yet everyone has no problem in computing power dissipated in circuits with incandescent lamp treating them as resistors, while when it comes to diodes the 'hard' exponential seems to create a mental block.

I just wanted to see how widespread this misconception is.

I've seen it taught that as a non-linear resistor for the purposes of calcuation, but it's not a resistor, it's a diode. Try changing the polarity and see what happens.
By your standard diodes are also resistors, or the B-E junction of a transistor is also a resistor, which is silly.

[Simon]

Dave, I locked the thread and this guy is taking the piss. PM from him:

Hi, have you had a breach in the system?
In the poll "do you think an LED is a resistor?" You wrote that the question was changed.

I just checked and the question is as I first formulated it. Has it been changed by someone else and then reverted back to its original form?