I like this answer. The only thing I would add is that when the fan blades are all stalled, it might seem then that drag and energy consumption should reduce, since there’s not much air moving. But in a cruel twist (fan pun intended) of aerodynamics, the useless spinning of stalled fan blades still causes parasitic drag. So not only does the fan not move air, it’s also consuming more energy than spinning a solid disk of the same moment-of-inertia.

When the engine fails for certain single-propeller aircraft, there’s sometimes a mechanism to lock the propeller to make it stop rotating, since it would otherwise “windmill” in the air and waste the previous kinetic energy that’s keeping the plane aloft. Or so I’m told.

It took me a few brain cycles to recognize that this was a spoon. Perhaps others were similarly momentarily confused.

I guess your nephew can start studying to become a network engineer now lol

In all seriousness, a 16 port managed switch exposes enough complexity to develop a detailed understanding of Ethernet and Layer 2 concepts, while not having to commit to learning illogical CLI commands to achieve basic functionality. 16 ports is also enough to wire up a non-trivial network, with ports to spare for exercising loop detection/protection or STP, but doesn’t consume a lot of electricity.

I would pair that switch with a copy of The All-New Switch Book, 2nd Edition to go over the networking theory. Yes, that book is a bit dated but networking fundamentals have not changed that much in 15 years. Plus, it can be found cheap, or on the high seas. It’s certainly not something to read cover-to-cover, since you can skip anything about ATM networks.

Then again, I think students might just simulate switch behaviors and topologies in something like GNS3, so no hardware needed at all.

The other comments correctly mention aspects like managing terrain and the width of railroads vs roadways. What I want to highlight is the development of road building methods at around the same time that metal-on-metal rail developed.

The 1800s were a wild time. Some clever folks figured out that they could put a contemporary steam engine – invented early 1700s; used only for stationary uses in lieu of water power – onto a wagonway. Wagonways are basically wooden or metal guides/flanges so that a horse-drawn wagon could be pulled along and stay perfectly centered on the path.

Up until this point in history, the construction of graded, flattened surfaces for moving goods didn’t change very much compared to what the Romans were doing with their roads. That is, a road had to be dug down and some soil removed, then backfilled with coarse material (usually large stones), and then a layer of smaller stones to try to approximate a smooth surface. The innovations the Roman introduced included a keen eye for drainage – freeze/thaw cycles destroy roads – and surveying methods (also to build things like aqueducts and canals). And concrete, of course.

But even the best built roads of that era were still prone to rutting, where each passing wagon slowly wears a groove into the road. Wooden wagons wider or narrower than the groove would suffer poor performance or outright break down. The wagonways sought to solve that issue by: 1) forcing all wagons to fit within the fixed guides on the sides, and 2) concentrate the grooves to exactly within the guides. The modern steel-on-steel railway takes this idea to its logical end.

An adhesive railroad seeks to be: all-weather, heavy duty, and efficient. Like Roman roads before it, all railways (except maybe on-street tramways) need to excavate the soil and build it up, usually being higher and wider than the rest of the land. It also minimizes the width of the earthworks, by being so compact and building upward. This sturdy base also provides a strong foundation to support heavy loads, preventing the steel rails from sinking or “rutting”. And finally, putting the wheel atop the rail makes for low-friction operation. Early wooden plateways sort-of did this, but they didn’t manage curves like how modern rails do.

All the while, instead of trying to support heavy wagons, another clever person sought to reinvent road building outright, postulating that if a surface could just spread out the load from light/medium traffic, then the soil beneath could be used as-is, saving a lot of earthworks. A gravel surface would meet this criteria, but gravel is not all-weather and can develop rutting. The key innovation was the use of binder (basically glue) to hold the surface together, such as tar. This sealing process meant the surface wouldn’t shift underneath traffic. This neatly avoided the issue of dust, made the surface water impermeable, and reduced road maintenance. So famous is this surfacing process that the inventor’s name can still be found in the surface for airport runways, despite runways always being excavated down to a significant depth.

So on one hand, rail technology developed to avoid all the pitfalls of 1700s roads. On the other hand, road surfacing developed to allow light/medium traffic roads to be economically paved for all-weather conditions. Both developments led to increased speed and efficiency in their domain, and networks of both would be built out.

Rail networks made it possible to develop the “streetcar suburbs” around major historical cities in the late 1800s. But on the same token, cheap road surfacing made it possible to build 1950s American suburbs, with wide, pedestrian-hostile streets sprawling in serpentine patterns. The fact that sealed roads are water impermeable has also substantially contributed to water pollution, due to increased rain runoff rather than absorbing into the underlying soil.

When doing research for this restoration, I did come across a suggestion about using the self cleaning feature on my oven. But some other comments suggested that self cleaning might put a lot of strain on the oven’s components, for a task which could also be achieved chemically.

So to see how my oven might behave, I set it to the highest temperature (550 F; 290 C) for 20 minutes. What happened was that the crud in the oven started smoking so badly that I had to cut the experiment short. Apparently I need to also clean my oven but I didn’t want to start a second project just to finish the first one. I’m lazy lol

So in my case, a hot oven was also a no-go. But a bonfire would have been awesome to do. For science, of course.

Thank you! One of these will be a gift, and I’m keeping the other one. My hope is that it achieves heirloom status, seeing as some online references suggest the larger skillet was manufactured sometime between 1935-1959. So just 35 more years and I can be sure it’ll be 100 years old!

For each seasoning cycle, I did the following:

• Arrange both skillets so that one edge leans on something inside the oven, so the skillets are face down but not parallel with the floor; this will drain excess oil, if any
• From cold, bring both skillets to 350 F (175 C) over 25 minutes
• When done, remove a skillet and wipe on/off corn oil onto every surface, then return to oven. A very thin sheen of oil. Repeat with other skillet.
• Set the oven for 350 F again, but now for 10 minutes
• When done, remove a skillet and wipe off any pools of oil, then return to oven. If the sheen of oil was thin, then there shouldn’t be any pools of oil anyway. Repeat with other skillet.
• Set the oven for 400 F (200 C) for 45 minutes
• When done, do not open the oven and let it cool on its own to room temperature over the next few hours

I’m personally very cautious about damage to/around batteries, due to !spicypillows@lemmy.world . At the very least, a photo might help depict the scale of the dent.

And while it might not be a spicy pillow right now, a damaged battery is more likely to turn spicy spontaneously. Replacement of the battery is, of course, the most risk-reducing move.

I once read a theory on an electricians forum about how the USA electrical code’s mandated maximum distance between adjacent outlets on a wall, coupled with the typical bedroom layout, as well as home builders trying to be as cheap as possible, led to only a single outlet being placed directly in the middle of the longest wall. This is also the most logical position for a bed, so the theory is that the bed pressing against the outlet over time was a contributing factor to electrical-related house fires.

I cannot find where I read that originally, and certainly the granularity of nationally-reported fire data is not sufficient to prove that theory. And while the electrical code’s distance requirements haven’t changed, more homes will now put enough outlets so the only one isn’t behind the bed.

I’m not trying to be ignorant, I’m just curious.

I think you’re in the right community! Don’t let anyone tell you to shy away from asking curious questions. (well, unless the question is also bigoted, illegal, baiting, sealioning, or otherwise disingenuous)

I’m not an electrician in any jurisdiction, but one answer for why two 2-meter (~6 ft) extension cords in series is inadvisable compared to a single 4 meter cord is that it’s not an apples-to-apples comparison. Longer cords necessarily have to be built differently than shorter cords, not only because of electrical codes (eg the NEC in USA) or product safety specs (eg UL, CSA) but also being well-designed for their expected use. There’s also the human aspect, which all good designs must account for as well.

Here in the USA, common extension cord lengths are ~2 m (6 ft), ~7.5 m (25 ft), ~15 m (50 ft), and ~30 m (100 ft). Of those cords, the common wire gauge used might be 18 AWG (~1 mm^2), 14 AWG (~2 mm^2), 16 AWG (~1.5 mm^2), and 12 AWG (~3.5 mm^2). I’ve intentionally rounded the metric units so they’re more analogous to common wire gauges outside the USA. Finally, the insulation used can be anything from “thin, indoor only” to “heavy, abrasion and sunlight resistant”. And while the USA technically has a boat-load of AC connectors, the grand majority will use the standard 2-pin or 3-pin 120v connector, formally known as NEMA 1-15 and NEMA 5-15 respectively. What this means is that chaining extension cords is both possible and somewhat common. The problem is one of mismatched designs.

From a cursory search on the website of a major USA home improvement store, the smallest wire gauge used for a 100 ft cable is 16 AWG. The largest is 10 AWG (nb: smaller numbers mean bigger wire). That thinner cable is marketed for outdoor use. The thicker cable indicates its use “indoor/outdoor” and for heavy-duty applications. It is also branded with a major power-tool company, which would be appropriate as power tools often draw high current.

Whereas looking at 6 ft extension cords, most are 16 AWG but a few were 18 AWG (thinner than 16) or 14 AWG (thicker). But I could not find any thicker cables than that, certainly nothing that uses 10 AWG (~6 mm^2). The “heavy duty” cables of this length also used only 16 AWG wire.

Because electrical resistance is additive in series, and because Ohm’s Law governs the voltage lost at the end of a cord, the use of insufficiently large conductors can cause voltage issues for high-current appliances. Appliances for USA-spec generally require 120 Volts +/- 10%, with utilities aiming to provide 120 Volts +/- 5% from the outlets. This means a “sufficient” power cord should not have a voltage drop of more than 6 volts, give or take. Of course, a high-current appliance will also cause a larger voltage drop than a low-current device, so we only consider the former case.

For a machine that draws 12 Amps attached to a 100 ft extension cord made of 18 AWG wire, the voltage drop would be 15 volts. This is bad for the machine, which now sees a lower voltage than expected. Had the cord been made of 12 AWG wire, the drop is an acceptable 3 volts.

So if you’re operating construction tools, it would be a terrible idea to use three random 6-ft cables, and you should instead use a single 25-ft cable. Even though it’s longer than you need, the fact is that most 25 ft cables use thicker conductors, which reduces the voltage drop overall.

But there’s also that peaky human factor. Sure, there would also be more connectors which could come loose, but the really pressing issue with daisy chained cords is when people do that indoors, because they only have light-duty 6 ft cables handy. And for that Christmas tree, they need to use attach three cables together to go beneath the hallway rug.

This is essentially the worst-case scenario: using thin conductor cords, with thin insulation, underneath very flammable household surfaces, which are also trodden upon by foot traffic. Every step on that cord weakens the insulation and fatigues the conductors. Over time, the conductor becomes thinner where it’s being fatigued, and this increases the voltage drop. An unfortunate result of a voltage drop is that it generates heat. For a cable which is uniformly thin, this heat is spread over the whole length. But for localized conductor damage, the heat is pin-point… directly under a flammable rug.

In the USA, some 3300 house fires started from an extension cord. Because these cords are not within the walls, they are usually beyond the control of often-strict building/electrical codes, something that’s been critiqued by a prominent YouTuber. The US CPSC even goes so far as to create memes to promote their messaging that space heaters – a common, high-current appliance – should not be used with extension cords or strips.

Of course, from an electrical perspective, even a ten-long chain of dinky extension cords would have no problem powering just a single LED night light. But it’s reasonable to ask: 1) is this just asking to be struck down by fate, 2) are there better alternatives like thicker/longer cords, and 3) why isn’t there an outlet where you need it?

(There’s also a scenario where too long or thin of an extension cord can cause a circuit breaker to fail to trip during a short circuit, but it’s fairly esoteric and this post is quite long now)

In short, the blanket recommendation to avoid daisy-chaining cords is to avoid the nasty and sometimes fatal results when that can go wrong, even with it might not always play out that way. There’s almost always something safer than can be done than daisy chaining.

You’re going to have to clarify what jurisdiction, since USA law is going to be vastly different than EU law, in the realms of product, medical devices, and public accommodations liability.

But if we did examine the USA, then we can find some generalized rules. For product liability – the responsibility of manufacturers and distributors of a tangible object – strict liability will lay when a product has an inherent defect (meaning it didn’t become defective after the initial sale) and this defect causes some sort of injury. Although this criteria doesn’t depend on the frequency of injuries, if a product is accumulating a body count, that’s usually a good sign that there’s a defect. Causality is also important to establish, as well as any mitigations that may have existed. On this front, a manufacturer might argue that the warnings in the instruction manual specifically advised against diving headlong into a 30 cm deep swimming pool. And although warning consumers to not do something may be somewhat effective at discharging liability, warnings alone do not prevent someone from trying a lawsuit anyway; the popular wisdom that the “pages of warnings” in manuals are written by lawyers is only partly true, since most manufacturer prefer repeat business by customers that are still alive.

Medical product liability is similar, but slightly different because medical products are built for a specific purpose but a doctor can instruct a patient to use it differently, if medically appropriate. If not used as instructed by the manufacturer, the manufacturer is usually off the hook, but the doctor might be liable for medical malpractice. Maybe. Doctor liability in the USA is framed within a “duty of care”, meaning that the doctor takes on a responsibility to act with a reasonable degree of skill and competency. The “standard of care” idea is related, in that it sets the floor for what is reasonable for all doctors. It is, for example, grossly negligent to a drunk doctor to examine a patient. Harms from such negligence can be litigated through a malpractice suit. But this doesn’t mean all harm is actionable. A successful appendectomy that results in blood sepsis is always going to be a possibility, even with the best infection controls in place. If all the staff discharged their duties within their training, then negligence does not attach. Also, malpractice is not something which can be waived, because even if a patient doesn’t sue, a doctor’s medical license can be suspended. Whereas the risks of a surgery can be described in detail to a patient, for informed consent.

Finally, public accommodations law sets the floor for how public and private businesses conduct themselves if they provide goods or services to the general public. Very prominently in this realm are accessibility requirements, which are rules that assure the disabled will not have undue burdens that able-bodied people wouldn’t face. The Americans with Disabilities Act (ADA) provides for very stiff fines for non-compliance, and because its objective was to set the standard, there is no provision for a “fix it ticket” approach for enforcement. That is to say, the ADA does not allow business owners to wait until a wheelchair user makes a complaint; they must follow the standard from day 1.

No doubt there is abuse of the liability laws – there’s nothing more American than filing “ambitious” lawsuits – and this is just a brief (and uncited, '“from the hip”) summary of possible areas of law that might answer your question. But I hope it gives you an idea of why a warning or sticker or sign might incur liability. Or at the very least, an unexpected lawsuit from left-field.