Incandescent bulbs in teaching

[Vanadium 50]

Why do you want 120/240 V bulbs? Miniature (flashlight) bulbs are still available, and cost under a dollar each.

While I question the utility of this, parts are available.

 

[PAllen]

I did not consider this for the simple reason that we do not say that in Swedish. We say essentially with-Sun and counter-Sun. The Sun is difficult to ignore unless young people stop going outside oh wait!

Is there a convention to look north??

 

[WWGD]

Is there a convention to look north??

Ah, the light

Is there a convention to look north??

Yes, their light bulb went on.

 

[ohwilleke]

This thread got me thinking. Incandescent light bulbs were soft banned (as in, cannot be sold anymore) in the EU in 2016 and - if my google-fu is to be trusted - last year in the US. If you go to any store selling bulbs, all of them are LED, which makes sense both from many perspectives.* We are soon going to face a generation of students who have never in their life seen an incandescent bulb. Meanwhile, they are typically used as examples in many physics classrooms.

A couple of discussion points:
How should teachers deal with this in the coming years?
Do we need to start introductory classes by explaining what an incandescent bulb is?
What happens with the laboratory experience when physics student labs run out of bulbs (they tend to break) and cannot obtain more?
Should we simply phase out the incandescent bulbs from the curriculum?


* Anecdotally, we were visiting my in-laws in Spain recently with temperatures soaring towards 40 °C. Their second home is sparingly used and therefore was still all incandescent bulbs. It felt slightly absurd to be in Spain in summer, inside with the window blinders shut in almost complete darkness as turning the lights on would heat the house too much. Took a day or two to change all the lights in the house for LEDs.

This is a new idea to physics education, since many parts of it (modern ideas of electromagnetism and thermodynamics, quantum mechanics, general and special relativity) are a comparatively young discipline, but other disciplines (like law and medicine and biology) are much more used to placing concepts like these in historical context and pedagogically, physics is going to have to start doing so to a greater extent. Imagine a lecture on the day of that unit starting something like this:

How can electromagnetism create light without chemical reactions?

Once upon a time the only way that this was done was with lightning, and that couldn't be created and controlled well enough to be safe and practical for everyday use. Man made lightening started with the Tesla coil.

Then, Edison invented the incandescent light bulb after intense trial and effort inspired by Europeans who were starting to assemble principles of electromagnetism that hadn't quite gelled into Maxwell's equations. These were easily mass produced from cheap materials, but were fragile, hot, and had to be changed often which is why your parents and grandparents have so many jokes about changing light bulbs that make no sense to you.

Then alternatives like halogen bulbs, neon lights, and florescent lights were invented. Halogen's produced a more eye friendly light at a greater cost but were also hot and short lived. Neon lights were expensive because they used rare noble gases and required expensive and fragile custom glass work. Florescent lights were cheap, lasted longer, and used less energy than incandescent lights, but flickered, were still fragile, and were hard on the eyes making you feel like you had a constant low grade headache, so they were mostly used in workplaces and public settings and not in homes.

Then Nick Holonyak (1962) invented the first mass produced light emitting diode (LED). His idea was initially confined to simple indicator lights. But in the late 20th century and early 21st century others came to realize that LEDs could be much more versatile and could produce the same number of lumens with far fewer watts, in part, because the generated far less heat.

Now, let's look at a historic replica of an incandescent light that was still in common use when your 50 year textbook that the school board refuses to replace was written.

 

[DaveE]

This is a new idea to physics education, since many parts of it (modern ideas of electromagnetism and thermodynamics, quantum mechanics, general and special relativity) are a comparatively young discipline, but other disciplines (like law and medicine and biology) are much more used to placing concepts like these in historical context and pedagogically, physics is going to have to start doing so to a greater extent.

I think in the future incandescent bulbs could be a good demo in the black body radiation section regardless of age. Otherwise, I see no reason to include obsolete devices in the curriculum. Much like the way I was taught about vacuum diodes in my late 1970's physics/EE courses. Teach these devices to elucidate basic concepts. Otherwise, update your lab demos as appropriate as things change. In my freshman EE lab we made LEDs and MOSFETs, not vacuum tubes or relays.

Personally, I think the history of electronic devices is really interesting. But it doesn't belong in the physical sciences department.

 

[ohwilleke]

I think in the future incandescent bulbs could be a good demo in the black body radiation section regardless of age. Otherwise, I see no reason to include obsolete devices in the curriculum. Much like the way I was taught about vacuum diodes in my late 1970's physics/EE courses. Teach these devices to elucidate basic concepts. Otherwise, update your lab demos as appropriate as things change. In my freshman EE lab we made LEDs and MOSFETs, not vacuum tubes or relays.

Personally, I think the history of electronic devices is really interesting. But it doesn't belong in the physical sciences department.

Maybe my perspective is a product of having studied this in the context of a liberal arts college education, instead of an electrical engineering program.

 

[jedishrfu]

Incandescent light bulbs will likely pop up in intro physics and possibly in labs too.

This post reminded me of my days at college in the 1970s in the Physics EM lab. We had some pretty antique equipment:
- large 6" knife switch mounted on an oak wood platform with two posts to attach wires
- large 12" potentiometer with a sliding switch mounted on a separate oak platform with connecting posts
- analog meters in oak boxes
- a large water-cooled U-shaped magnet that was too big to carry, about the size of a large toaster oven with tubing for water supply hookup.
- spectroscope to view the line split

We used them to recreate the Zeeman effect, likely using much of the same equipment Zeeman used in 1896.

I felt I was in Frankenstein's lab. We were warned to:
- hookup the water supply and ensure it's flowing through the magnet
- hook up the DC power supply,
- ensure the potentiometer was at maximum resistance, and then
- close the knife switch

DON'T TOUCH ANYTHING! while doing the experiment

REVERSE THE PROCESS to power down the magnet

Reverse the process to power down the magnetic field via the potentiometer. Don't just open the knife switch unless you want to see a nice 6" electrical arc.

It was terrifying to me. I was shocked as a 4-year-old kid while running my hand down a frayed electrical cord that my father had just removed from a lamp and that I decided to plug into a live outlet nearby. My mom freaked out and quickly covered my hand in butter circa 1956.

 

[Drakkith]

While not as practical, coil stovetops are a great idea for demonstrating the same principles as incandescent bulbs. You can even cook some soup while your students learn!

 

[Orodruin]

While not as practical, coil stovetops are a great idea for demonstrating the same principles as incandescent bulbs. You can even cook some soup while your students learn!

I somehow feel that coil stovetops may be even more obsolete than incandescent bulbs though

 

[Drakkith]

I somehow feel that coil stovetops may be even more obsolete than incandescent bulbs though

Perhaps, but at least you can still buy them everywhere!

 

[Orodruin]

at least you can still buy them everywhere!

Can you though? I just had a look at some of the online stores selling integrated stoves in Sweden. It is all induction, induction, induction, induction, gas, induction, induction, induction.

 

[NTL2009]

Just remember, without incandescent light bulbs, there likely would have been no Hewlett Packard, and no Disney Fantasia.

https://www.hewlettpackardhistory.com/item/a-deal-with-disney/

There are probably some who don't know of the connection (w/o digging deeper into your link), but Bill Hewlett used an incandescent light bulb in HP's first product, the HP200A audio oscillator to stabilize the output and keep distortion low (from wiki - 'Rb' is the resistance of the light bulb):

Rb self heats and increases the negative feedback which reduces the amplifier gain until the point is reached that there is just enough gain to sustain sinusoidal oscillation without over driving the amplifier.

If R1 = R2 and C1 = C2 then at equilibrium Rf/Rb = 2 and the amplifier gain is 3. When the circuit is first energized, the lamp is cold and the gain of the circuit is greater than 3 which ensures start up.

The positive temperature coefficient of (once) common/cheap incandescent bulbs made them useful in many ways. Put one in series with a power supply output, and you can get some current limiting, or a somewhat constant current source over a small range.

I once worked on a large digital board test system that protected its digital outputs with very small series light bulbs (hundreds of them). The bulb would have a low R under normal TTL/CMOS input currents, but quickly heat up and increase R if there were a short on the Board Under Test. I'm not sure about those bulbs, but a (once) typical 60~100 W 120V incandescent bulb would have about a 10:1 shift in impedance between cold (room temp) and full operating temperature. So that 'feature' also provided the higher gain at start up for the HP200A oscillator. And a large in-rush current when switched on in a home setting, which is why bulbs would often burn out just as you turned them on.

That's quite a bit of benefit from a simple, cheap (and common at the time) device! BTW, it was a 6W 120V bulb, so about the same as a recent incandescent night-light bulb.

 

[ohwilleke]

I somehow feel that coil stovetops may be even more obsolete than incandescent bulbs though

They're considering banning gas stoves which will make them more common, not less. Coil stoves are almost universal in cheap U.S. apartments and you can also buy a separate plug in version (my in-laws use them to simmer meat on their porch for long periods of time while leaving their main stove unburdened).

 

[gmax137]

They're considering banning gas stoves which will make them more common, not less.

ugh, don't get me started...

 

[WWGD]

Well, I just bought a lamp that lights up without any lightbulb. And the surface that lights up stays at room temperature

 

[Drakkith]

Well, I just bought a lamp that lights up without any lightbulb. And the surface that lights up stays at room temperature

LED?

 

[WWGD]

LED?

Yes. It had me at $2.50. Though I have no idea where the heat sink is.

 

[Swamp Thing]

I started my career at a company that made electronic test instruments. One of those was an audio signal generator. It used a Wien bridge oscillator as the basic source.

Of course, these circuits would produce unacceptable harmonic output if the oscillator was allowed to build up to a level limited only by supply voltage and other nonlinearities. So it contained a deceptively simple but highly effective level control. The oscillator's feedback network contained a very tiny low-power filament lamp (which may even have been designed specifically for such purposes, IDK). As the oscillation built up, the lamp would heat up, its resistance would increase, and the feedback factor would be brought down.

I remember that they tried to replace this with other ALC mechanisms but finally decided to stick with that little ole lamp.

 

[AlexB23]

This thread got me thinking. Incandescent light bulbs were soft banned (as in, cannot be sold anymore) in the EU in 2016 and - if my google-fu is to be trusted - last year in the US. If you go to any store selling bulbs, all of them are LED, which makes sense both from many perspectives.* We are soon going to face a generation of students who have never in their life seen an incandescent bulb. Meanwhile, they are typically used as examples in many physics classrooms.

A couple of discussion points:
How should teachers deal with this in the coming years?
Do we need to start introductory classes by explaining what an incandescent bulb is?
What happens with the laboratory experience when physics student labs run out of bulbs (they tend to break) and cannot obtain more?
Should we simply phase out the incandescent bulbs from the curriculum?


* Anecdotally, we were visiting my in-laws in Spain recently with temperatures soaring towards 40 °C. Their second home is sparingly used and therefore was still all incandescent bulbs. It felt slightly absurd to be in Spain in summer, inside with the window blinders shut in almost complete darkness as turning the lights on would heat the house too much. Took a day or two to change all the lights in the house for LEDs.

Guys, you can build incandescent bulbs using graphite pencils and a car battery. But yes, incandescent bulbs were banned in 2023 in the USA. LEDs are more efficient, but if you need incandescent bulbs, old bike lights could work, same with oven lights, as LEDs would overheat in the oven.

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