If a filament is suspended in a perfect vacuum, do we agree that the only way it can lose heat is by radiation? (IR + light)
I was thinking about the implications of a coiled filament. It seems to me that by coiling the filament, it cannot radiate from half its surface (the IR radiation on the inside of the coil is balanced by the IR radiation coming in from the opposite side). So a coiled filament will run hotter than the same length of filament that has not been coiled. - Which in turn means that a coiled filament could be made from thicker wire, and might therefore last longer... ?
If they were under vacuum, the glass envelope would have to be much more robust, plus it makes the manufacturing far more complex. (As vacuum tube manufacturing shows us!) Instead of pulling a high vacuum they just shove a hose in and pump in the inert gas, which pushes out the air. Since it’s at ambient pressure, it can then be “lazily” sealed off without the complexity of having to maintain high vacuum during pinch-off.
I guess so, maybe. But it doesn’t matter, since incandescent light bulbs don’t use vacuums. The envelopes are filled with inert gas at roughly ambient pressure, such that the glass envelope isn’t under any real pressure. If they were under vacuum, the glass envelope would have to be much more robust, plus it makes the manufacturing far more complex. (As vacuum tube manufacturing shows us!) Instead of pulling a high vacuum they just shove a hose in and pump in the inert gas, which pushes out the air. Since it’s at ambient pressure, it can then be “lazily” sealed off without the complexity of having to maintain high vacuum during pinch-off.
There were some incandescent bulbs with built in diodes to allow the use of a shorter and thicker filament for a given wattage, often marketed as "solid state enhanced". They did not achieve much popularity since they appeared around the time CFLs became affordable.
Surprisingly many people will argue there is no such thing as planned obsolescence...
And people will argue that it exists where it doesn't, or where it's just incompetence or cost-cutting. "Yeah, maaaaan, they had a carburetor back in the 70's that got 100MPG maaaaaan. But they don't want you to know."
Sure, but that's not what was being discussed in the video: we are talking about hard-core planned obsolescence.
I can see it could be hard for e.g. an Apple fan-boi to admit they are being taken advantage of this way, but nevertheless, that is what is happening to them.Or maybe it’s because it’s actually not. The useful lifespans of Apple products is well above average, and this has been the case since the 80s.* Apple provides OS updates for its phones and tablets for 5+ years, far above the 0-2 years typical in the Android world. (My iPad is from 2014 and still gets OS updates, and is still more than snappy enough for daily use. My 2015 iPhone 6S running the current iOS is nearly as snappy as my year-old SE. I only upgraded because I couldn’t get replacement parts quickly enough due to COVID delays, and my screen was cracked.)
*Through the mid 2000s, researchers continuously found that Windows PCs were replaced after an average of 3 years, while the average Mac was replaced after 4-5 years. Between the longer lifespan and the dramatically higher resale value, the higher up-front cost was more than compensated. Since then, the average useful lives of both PCs and Macs has risen a lot, but the much higher resale value of used Macs is still the case.
I haven't seen any evidence that Apple products don't last as long as their competitors.
I haven't seen any evidence that Apple products don't last as long as their competitors.Their cables last a few months in average and are sold at huge premium. Competitor cables last for years and are much cheaper. Before they removed user ratings:
The switch to more advanced bulbs that have less "real world" life and at higher cost might be considered related to Planned Obsolescence: basically, needlessly increase the complexity of a product so you can charge more for it.
This works best of all if you can lobby to have laws passed that bans the simple and inexpensive solution that you don't think is making you enough money... especially if you think the public would not accept price rises on the existing, simpler product!
I could make the same statement about electronically commutated motors which replaced shaded pole motors in refrigerator evaporators because of EPA requirements. I have never had one of these shaded pole motors fail, but I have had to replace the electronically commutated motor in my new refrigerator 6 times now in 10 years, and they cost $30 each.
I could make the same statement about electronically commutated motors which replaced shaded pole motors in refrigerator evaporators because of EPA requirements. I have never had one of these shaded pole motors fail, but I have had to replace the electronically commutated motor in my new refrigerator 6 times now in 10 years, and they cost $30 each.
I'm kind of surprised to hear they're THAT bad. Did you look into what actually failed? I've had the shaded pole motors fail before but it was only the bearings. My friend had a fridge in a rental house that would make weird chirping noises, I immediately identified it as bearing failure in the evaporator fan motor but they had no clue what it was.
The switch to more advanced bulbs that have less "real world" life and at higher cost might be considered related to Planned Obsolescence: basically, needlessly increase the complexity of a product so you can charge more for it.
This works best of all if you can lobby to have laws passed that bans the simple and inexpensive solution that you don't think is making you enough money... especially if you think the public would not accept price rises on the existing, simpler product!
I could make the same statement about electronically commutated motors which replaced shaded pole motors in refrigerator evaporators because of EPA requirements. I have never had one of these shaded pole motors fail, but I have had to replace the electronically commutated motor in my new refrigerator 6 times now in 10 years, and they cost $30 each.
I haven't seen any evidence that Apple products don't last as long as their competitors.Their cables last a few months in average and are sold at huge premium. Competitor cables last for years and are much cheaper. Before they removed user ratings:
I haven't seen any evidence that Apple products don't last as long as their competitors.Their cables last a few months in average and are sold at huge premium. Competitor cables last for years and are much cheaper. Before they removed user ratings:Oh, I'd forgotten about the crappy cables, which I believe were due to Apple going halogen free and nothing to do with planned obsolescence, so it didn't enter my mind. Going by the dates on that screenshot, none of the complaints are recent, so hopefully it's been resolved now. I've had similar problems with halogen free cables, on a project I've worked on.
new iPhone SE, iPhone Xs, AirPods, whatever -- have been quite robust, certainly all much better than off-brand cables which last a week.
Yeah the shaded pole motors I've had fail were all at least 15 years old. I'm still surprised these are that bad, I'd be curious to look inside one and see what is actually failing, it may be a good opportunity to improve the design. There is no inherent reason a motor like that can't be reliable, I mean the ubiquitous brushless DC muffin fans often last many years and in every one of those I can recall having fail it was bearings.
Yeah the shaded pole motors I've had fail were all at least 15 years old. I'm still surprised these are that bad, I'd be curious to look inside one and see what is actually failing, it may be a good opportunity to improve the design. There is no inherent reason a motor like that can't be reliable, I mean the ubiquitous brushless DC muffin fans often last many years and in every one of those I can recall having fail it was bearings.
The electronics are potted in epoxy where the coil would be on a shaded pole motor with what I suspect is an exposed 3 wire hall effect sensor to track rotation. The oldest ones I have seen used shaded pole motor armatures without the shorted turns.
Because the motors still turn, but at low speed, I suspect the rotor may have demagnetized. Whatever the problem, over a 10 year period they have an appalling reliability and cost effectiveness.
If they were under vacuum, the glass envelope would have to be much more robust, plus it makes the manufacturing far more complex. (As vacuum tube manufacturing shows us!) Instead of pulling a high vacuum they just shove a hose in and pump in the inert gas, which pushes out the air. Since it’s at ambient pressure, it can then be “lazily” sealed off without the complexity of having to maintain high vacuum during pinch-off.Not true. Air is pumped out thus creating vacuum inside and only then inert gas is filled.
It actually isn't as simple as just "shoving a hose in", it's necessary to draw a fairly hard vacuum and bake out impurities before backfilling with inert gas. Getting lazy with this process is one reason a lot of cheap bulbs don't last very long. The inert gas fill is done for only one reason, to reduce the evaporation of tungsten by increasing the pressure inside the bulb, it doesn't save any manufacturing effort.
Lots of bulbs do use vacuums, typically below about 40 watts, this is because as the wattage goes down and the filament is thinner, the convective losses of a gas fill become much more pronounced. The pressure is not an issue at all, vacuum tubes for example are obviously vacuum filled and the envelopes on those are not any thicker than light bulbs.
I suspect that if they were under hard vacuum, they’d be too fragile for general use. That one can evacuate it to a vacuum during manufacturing doesn’t mean it could hold up to household manhandling.
Or maybe it’s because it’s actually not. The useful lifespans of Apple products is well above average, and this has been the case since the 80s.* Apple provides OS updates for its phones and tablets for 5+ years, far above the 0-2 years typical in the Android world. (My iPad is from 2014 and still gets OS updates, and is still more than snappy enough for daily use. My 2015 iPhone 6S running the current iOS is nearly as snappy as my year-old SE. I only upgraded because I couldn’t get replacement parts quickly enough due to COVID delays, and my screen was cracked.)I haven't seen any evidence that Apple products don't last as long as their competitors. The consensus seems to be they're fairly reliable. Apple frequently get criticised for making new products incompatible, with accessories designed for older products and updates which deliberately slow the device down.
Quote*Through the mid 2000s, researchers continuously found that Windows PCs were replaced after an average of 3 years, while the average Mac was replaced after 4-5 years. Between the longer lifespan and the dramatically higher resale value, the higher up-front cost was more than compensated. Since then, the average useful lives of both PCs and Macs has risen a lot, but the much higher resale value of used Macs is still the case.That's not been the case for a long time though. I've had the same computer for nearly five years and it was nine years old, when I got it. The only upgrades were the RAM and a solid state hard drive.
Oh, I'd forgotten about the crappy cables, which I believe were due to Apple going halogen free and nothing to do with planned obsolescence, so it didn't enter my mind. Going by the dates on that screenshot, none of the complaints are recent, so hopefully it's been resolved now. I've had similar problems with halogen free cables, on a project I've worked on.
I suspect that if they were under hard vacuum, they’d be too fragile for general use. That one can evacuate it to a vacuum during manufacturing doesn’t mean it could hold up to household manhandling.Vacuum does not suck anything in, it's just an empty space. Stress is created by pressure difference. And it's only a 1 bar pressure from the outside. It does not matter how hard vacuum is. Complete vacuum VS 1% of air left makes virtually no difference in how much stress glass will experience.
but it certainly would reduce their maximum drop distance, for example.