Bulbs connected in series. Physics doesn't add up

[TimFox]

Actually, this joke series is a reference to a BBC comedy, "Fawlty Towers", series 2, episode 6.

[tooki]

There is an anecdote circulating on-line about a new employee who was told not to spell "hamster" as "hampster" but refused to change because that's the way she spelled it.

[MrAl]

You're getting there, but while it can be said that a non-linear material/device has resistance, it is confusing to the point of being meaningless to measure it in Ohms. Ohm's has a meaning in the context of Ohm's Law, and that requires a linear material/device.
 

Are you sure about that?

Resistance is stated in units of Ohms, it does not matter where it comes from.  Negative resistance is a special case.
It does not have to follow Ohm's Law, but it can still be stated in units of Ohms.
Resistance dissipates energy while something that stores energy like a capacitor or inductor does not have resistance it only stores energy.
This means we can say a diode has resistance at a certain point and therefore dissipates energy, even though it does not follow Ohm's Law.
This we can have a statement about the unit Ohms without the device necessarily following the Ohm's Law proper.
I'm pretty sure you know this but you stated it a little differently.

We might also talk about the modernization of Ohm's Law, but that would probably just cause more confusion.

[MrAl]

Ohm's has a meaning in the context of Ohm's Law, and that requires a linear material/device.

You view the Ohm unit in a narrow context, considering it solely as a concept of resistance that applies meaningfully only to linear components with Ohmic resistance. In contrast, I see the Ohm unit in a broader context - as the ratio of voltage to current or the ratio of electric field strength to magnetic field strength. This ratio reflects the constant relationship for linear components with Ohmic resistance (which we know as classic Ohm's law), but it also applies to both linear and nonlinear components at selected voltage and current levels. This perspective, while extending beyond the classical interpretation of Ohm's Law, continues to address the same fundamental essence expressed as the relationship between voltage and current. It emphasizes the intrinsic physical nature of this relationship, which significantly impacts the efficiency of energy transfer from the source to the receiver.

For example, the characteristic impedance of the environment surrounding an antenna is also expressed in Ohms. However, this impedance is varying within the near-field region and, even in the far-field region it depends on the properties of the surrounding environment. Does this mean that we cannot express it in Ohms?

I believe he stated that incorrectly.  Ohms is a unit while Ohm's Law is a relationship between measurements that applies in some cases.
Ohm's Law is not a true law it is an empirical law, but the unit of Ohms is always the unit of Ohms whether it follow what we call Ohm's Law or not.  When we have resistance we see energy being absorbed.  That's a fundamental physical concept.

[tggzzz]

You're getting there, but while it can be said that a non-linear material/device has resistance, it is confusing to the point of being meaningless to measure it in Ohms. Ohm's has a meaning in the context of Ohm's Law, and that requires a linear material/device.
 

Are you sure about that?

Resistance is stated in units of Ohms, it does not matter where it comes from.  Negative resistance is a special case.
It does not have to follow Ohm's Law, but it can still be stated in units of Ohms.
Resistance dissipates energy while something that stores energy like a capacitor or inductor does not have resistance it only stores energy.
This means we can say a diode has resistance at a certain point and therefore dissipates energy, even though it does not follow Ohm's Law.
This we can have a statement about the unit Ohms without the device necessarily following the Ohm's Law proper.
I'm pretty sure you know this but you stated it a little differently.

We might also talk about the modernization of Ohm's Law, but that would probably just cause more confusion.

You make some valid points, but...
Negative resistance isn't mathematically a different case.
Resistance is a susbset of impedance, where the reactive component is zero. Both are quantified in Ohms.

[TimFox]

One case where the incremental or AC resistance (derivative dV/dI at a given operating point) is useful is in the calculation of Johnson (thermal) noise.
Since noise is a small variation about the equilibrium condition, any real (non-reactive) component of the impedance (R + jX) will generate the same noise as an ohmic resistor in the equivalent circuit.

[Ice-Tea]

Dude asks a question about lightbulbs.

We're now on thermal noise and complex calculus 

Oh, and the OP has long since left the building...

[TimFox]

Physics is hard:  live with it.
Note that the OP's question title includes "Physics doesn't add up".
Some of us were explaining the physics.

[radiolistener]

Dude asks a question about lightbulbs.

We're now on thermal noise and complex calculus 

Hold on, we haven't even gotten to relativistic corrections and quantum effects yet - the real fun is still ahead! 

[m k]

Is it time again, seems that my R doesn't include time, it's a point like thing and can't have variations.
If it changes to Z it's still sort of a moment, it doesn't include any waveform.

[BeBuLamar]

If you say the light bulb is non linear then just about any resistance is non linear. I don't know of a conductor that doesn't change its resistance with temperature. Most of the time it's insignificant because the temperature changes are too small but there always is a change in resistance with a change in temperature.

[TimFox]

Yes, conductive media usually have a measurable temperature co-efficient.
However, it is possible to externally control the temperature of the resistive element, and at low power the self-heating should be negligible.
As I pointed out near the beginning of this thread, Ohm's Law is an approximation that is usually useful, but it is not strictly exact:  many resistors exhibit a voltage co-efficient of resistance (unrelated to temperature), but it is rarely specified on the data sheet.
I have seen physically small (0603 and 0805 SMT) high-value resistors where the resistance changes by > 0.1% at constant temperature for only 10 V applied to 50 megohms.
Lower-value resistors in reasonable packages (e.g., RN60 metal film TH resistors) are more linear.
Light bulbs are extremely non-linear, treated as components, over their usual operating voltage and current range, as shown in measurements reported above.

[tggzzz]

Is it time again, seems that my R doesn't include time, it's a point like thing and can't have variations.
If it changes to Z it's still sort of a moment, it doesn't include any waveform.

Resistors do have a time dependence: a standard real pain in the backside are carbon composition resistors that drift higher over the decades

Resistors also have a voltage dependence. I have some high quality "resistance transfer standards" resistors that were measured in a calibration lab; for one the label indicates:
100V 1.025
200V 1.027
500V 1.001

TOhms, that is

No, those connectors aren't BNC, and no, I haven't opened the case.

[MrAl]

Actually, this joke series is a reference to a BBC comedy, "Fawlty Towers", series 2, episode 6.

That was a good one.
Of the foreign tv shows, I also liked Monte Python of course, and Poirot, but my favorite by far was Coupling which was outstanding.

[MrAl]

If you say the light bulb is non linear then just about any resistance is non linear. I don't know of a conductor that doesn't change its resistance with temperature. Most of the time it's insignificant because the temperature changes are too small but there always is a change in resistance with a change in temperature.

I think there is a difference between a light bulb filament and a regular resistor or even copper wire.  That's because we do not normally use just a regular resistor or copper wire until they get red or white hot.  The filament and it's enclosure is made to keep it hot and stay hot, while with the others we only use them up to a certain temperature.   Of course, there is the fusing temperature which we take into account for fuses, but once the fuse blows that's about as big as a change in resistance as we can get.  If you want to call that a nonlinear resistance that's up to you

[MrAl]

Dude asks a question about lightbulbs.

We're now on thermal noise and complex calculus 

Oh, and the OP has long since left the building...

Well, imagine we are all sitting in a cafe' or dining room or board room and someone walks in and asks a question.  We answer that question, then he leaves.  Do we suddenly forget all about that and go on to sip coffee or tea and just stay completely silent?  I don't think so.  If the question is interesting enough, it may lead to a longer discussion among us.  That's just what being social is all about.  If you would like to stay silent however, that is always your choice, but there's no good reason to try to stop others from continuing the discussion.

This topic happens to be one of the most controversial I've seen on the web even though it shouldn't be.  It's just about the way humans deal with physics.  We are constantly coming up with new ways to abbreviate the complex to make it faster to deal with, and in the process making it a little more obscure for someone who is not in the know.  It's both a blessing and a curse.

[m k]

Resistors also have a voltage dependence. I have some high quality "resistance transfer standards" resistors that were measured in a calibration lab; for one the label indicates:
100V 1.025
200V 1.027
500V 1.001

TOhms, that is

But shouldn't there be an indicator that the value includes time.
Maybe tOhms, but would yours then be tTOhms or TtOhms, and should there then be more than one value.

[Ice-Tea]

Dude asks a question about lightbulbs.

We're now on thermal noise and complex calculus 

Oh, and the OP has long since left the building...

Well, imagine we are all sitting in a cafe' or dining room or board room and someone walks in and asks a question.  We answer that question, then he leaves. 

This is the beginner section of the forum. For simple questions and simple answers.

To further your analogy: imagine the guy asking the question still sitting at the table, wondering what the hell just happened, feeling like all the fun is being sucked out of his simple experiment, feeling unwelcome at the table, considering never to ask a question with these clowns again and contemplating if maybe electronics isn't for him/her after all.

No offense and all that, but as an educational endeavour you guys are kinda missing the mark.

[IanB]

This is the beginner section of the forum. For simple questions and simple answers.

To further your analogy: imagine the guy asking the question still sitting at the table, wondering what the hell just happened, feeling like all the fun is being sucked out of his simple experiment, feeling unwelcome at the table, considering never to ask a question with these clowns again and contemplating if maybe electronics isn't for him/her after all.

No offense and all that, but as an educational endeavour you guys are kinda missing the mark.

I thought the same thing. Threads in the beginner section should not get derailed and taken off into the weeds. The goal should be to help the person posting and not conduct private discussions.

[TimFox]

The balance here is not to leave incorrect information to confuse the OP.
(I know:  somebody's wrong on the internet.)

[tggzzz]

The balance here is not to leave incorrect information to confuse the OP.
(I know:  somebody's wrong on the internet.)

... and not to leave incorrect information to confuse other people that randomly bumble into the conversation later on
... and to (attempt to) prevent yet another outbreak of misinformation

[BeBuLamar]

Dear community

I am a beginner learning the basics of electronics. Currently I read "Easy Electronics" by Charles Platt. I am making the experiments from the book to make sure I get the same results. I am on the page 9 and already have a question I cannot answer myself.
The book says when two identical components are in parallel, then the current doubles. Consequently, when two identical components are in series, they create twice as much resistance for the current and there will be half as much current. Sounds logical.
I have proved experimentally that "when two identical components are in parallel, then the current doubles" and I have no problems with that. However, something weird happens "when two identical components are in series", because they actually do not create twice as much resistance as promised. In fact, the resistance increases less than 50%!
In other words, the question is: Why is the resistance not doubled when I put two identical cmponents in series?

Below are details of the experiments, images and drawings. Although I tried to be as thorough as possible, I imagine there may be some gaps, so any relevant questions and comments are welcome.

Equipment used
DC Power Supply
2x 2.5V bulbs
2x bulb holders


Notes
For unknown reason the resistance if the same type bulbs significantly differs -  from 1.3 to 4 Ω. I selected 2 bulbs with 1.9 Ω.
Bulb holders are identical.

Experiment 1
One 2.5V bulb consumes 178mA. Verified with both bulbs.

Experiment 2
Two 2.5V bulbs in parallel consume 353mA. 176.5mA per bulb which is pretty close to the current for one bult from Experiment 1(178mA)!

Experiment 3
What will happen if bulbs put in series? 175mA as half of the current? Half of that like 87.5mA? Wrong! The current is 127mA. And this figure puzzles me. How is it possible?

Can you do the experiment 3 again but this time with 5V instead of 2.5V? I bet it would come out right.

[MrAl]

Dude asks a question about lightbulbs.

We're now on thermal noise and complex calculus 

Oh, and the OP has long since left the building...

Well, imagine we are all sitting in a cafe' or dining room or board room and someone walks in and asks a question.  We answer that question, then he leaves. 

This is the beginner section of the forum. For simple questions and simple answers.

To further your analogy: imagine the guy asking the question still sitting at the table, wondering what the hell just happened, feeling like all the fun is being sucked out of his simple experiment, feeling unwelcome at the table, considering never to ask a question with these clowns again and contemplating if maybe electronics isn't for him/her after all.

No offense and all that, but as an educational endeavour you guys are kinda missing the mark.

It seems he left the board room, or should I say instead he left the bored room

While people may agree with that stand and I know people that would, I cannot agree fully because this is not just an electronics site or an educational site it's partly social media.  When people start talking, it's often good to read because lots of information comes out of it.
I do have to agree that we don't want to go too far with this though, but then usually we don't.  We don't usually get into quantum physics and partial differential equation solutions and stuff like that.

Maybe we should let the original poster decide, and if he does not come back then no harm done anyway.  It's true though that he may get overwhelmed, but then where do we really draw the line.  It's hard to say because some 'beginners' are not really beginners, although (and this is a little funny) some experts are not really experts either (ha ha).

If you like you can try to come up with a criterion for how much information is too much.  You'll have to describe this in detail though.  It could make a difference to newcomers one day.

[Xena E]

I downloaded the book and it puts itself forward as being elementary but then uses filament lamps in series and parallel to illustrate a badly made point, which is a bit crappy, unless the author didn't understand that filament lamps are not ohmic devices either. Very misleading to the OP from the very start.

It also suggested the reader uses nail clippers to crop component leads. 

[BeBuLamar]

When you do experiment 1 you can see already that your measurement doesn't make sense.
At 2.5V and you have 178mA then the resistance must be 14Ohms but when you measured the resistance when it was cold you got 1.9 Ohms. The resistance increased by almost 10 fold when it's hot.