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I. My dad emigrated from Colombia to North America when he was 18 looking looking for a better life. For my brother and I that meant a lot of standing outside in the cold. My dad’s preferred method of improving his lot was improving lots, and my brother and I were “voluntarily” recruited to help working on the buildings we owned. That’s how I came to spend a substantial part of my teenage years replacing fences, digging trenches, and building flooring and sheds. And if there’s one thing I’ve learned from all this building, it’s that reality has a surprising amount of detail. This turns out to explain why its so easy for people to end up intellectually stuck. Even when they’re literally the best in the world in their field. Consider building some basement stairs for a moment. Stairs seem pretty simple at first, and at a high level they are simple, just two long, wide parallel boards (2” x 12” x 16’), some boards for the stairs and an angle bracket on each side to hold up each stair. But as you actually start building you’ll find there’s a surprising amount of nuance. The first thing you’ll notice is that there are actually quite a few subtasks. Even at a high level, you have to cut both ends of the 2x12s at the correct angles; then screw in some u-brackets to the main floor to hold the stairs in place; then screw in the 2x12s into the u-brackets; then attach the angle brackets for the stairs; then screw in the stairs. Those goddamn stairs. Next you’ll notice that each of those steps above decomposes into several steps, some of which have some tricky details to them due to the properties of the materials and task and the limitations of yourself and your tools. The first problem you’ll encounter is that cutting your 2x12s to the right angle is a bit complicated because there’s no obvious way to trace the correct angles. You can either get creative (there is a way to trace it), or you can bust out your trig book and figure out how to calculate the angle and position of the cuts. You’ll probably also want to look up what are reasonable angles for stairs. What looks reasonable when you’re cutting and what feels safe can be different. Also, you’re probably going to want to attach a guide for your circular saw when cutting the angle on the 2x12s because the cut has to be pretty straight. When you’re ready to you will quickly find that getting the stair boards at all the same angle is non-trivial. You’re going to need something that can give you an angle to the main board very consistently. Once you have that, and you’ve drawn your lines, you may be dismayed to discover that your straight looking board is not that straight. Lumber warps after it’s made because it was cut when it was new and wet and now it’s dryer, so no lumber is perfectly straight. Once you’ve gone back to the lumber store and gotten some straighter 2x12s and redrawn your lines, you can start screwing in your brackets. Now you’ll learn that despite starting aligned with the lines you drew, after screwing them in, your angle brackets are no longer quite straight because the screws didn’t go in quite straight and now they tightly secure the bracket at the wrong angle. You can fix that by drilling guide holes first. Also you’ll have to move them an inch or so because it’s more or less impossible to get a screw to go in differently than it did the first time in the same hole. Now you’re finally ready to screw in the stair boards. If your screws are longer than 2”, you’ll need different ones, otherwise they will poke out the top of the board and stab you in the foot. At every step and every level there’s an abundance of detail with material consequences. It’s tempting to think ‘So what?’ and dismiss these details as incidental or specific to stair carpentry. And they are specific to stair carpentry; that’s what makes them details. But the existence of a surprising number of meaningful details is not specific to stairs. Surprising detail is a near universal property of getting up close and personal with reality. You can see this everywhere if you look. For example, you’ve probably had the experience of doing something for the first time, maybe growing vegetables or using a Haskell package for the first time, and being frustrated by how many annoying snags there were. Then you got more practice and then you told yourself ‘man, it was so simple all along, I don’t know why I had so much trouble’. We run into a fundamental property of the universe and mistake it for a personal failing. If you’re a programmer, you might think that the fiddliness of programming is a special feature of programming, but really it’s that everything is fiddly, but you only notice the fiddliness when you’re new, and in programming you do new things more often. You might think the fiddly detailiness of things is limited to human centric domains, and that physics itself is simple and elegant. That’s true in some sense – the physical laws themselves tend to be quite simple – but the manifestation of those laws is often complex and counterintuitive. II. Boiling A Watched Pot Consider the boiling of water. That’s straightforward, water boils at 100 °C, right? Well the stairs seemed simple too, so let’s double check. Put yourself in the shoes of someone at the start of the 1800’s, with only a crude, unmarked mercury thermometer, trying to figure the physics of temperature. Go to your stove, put some water in a pot, start heating some water, and pay attention as it heats. (I suggest actually doing this) The first thing you’ll probably notice is a lot of small bubbles gathering on the surface of the pot. Is that boiling? The water’s not that hot yet; you can still even stick your finger in. Then the bubbles will appear faster and start rising, but they somehow seem ‘unboiling’. Then you’ll start to see little bubble storms in patches, and you start to hear a hissing noise. Is that Boiling? Sort of? It doesn’t really look like boiling. The bubble storms grow larger and start releasing bigger bubbles. Eventually the bubbles get big and the surface of the water grows turbulent as the bubbles begin to make it to the surface. Finally we seem to have reached real boiling. I guess this is the boiling point? That seems kind of weird, what were the things that happened earlier if not boiling. To make matters worse, if you’d used a glass pot instead of a metal one, the water would boil at a higher temperature. If you cleaned the glass vessel with sulfuric acid, to remove any residue, you’d find that you can heat water substantially more before it boils and when it does boil it boils in little explosions of boiling and the temperature fluctuates unstably. Worse still, if you trap a drop of water between two other liquids and heat it, you can raise the temperature to at least 300 °C with nothing happening. That kind of makes a mockery of the statement ‘water boils at 100 °C’. It turns out that ‘boiling’ is a lot more complicated than you thought. This surprising amount of detail is is not limited to “human” or “complicated” domains, it is a near universal property of everything from space travel to sewing, to your internal experience of your own mind. III. Invisible vs. Transparent Detail And Getting Intellectually Stuck Again, you might think ‘So what? I guess things are complicated but I can just notice the details as I run into them; no need to think specifically about this’. And if you are doing things that are relatively simple, things that humanity has been doing for a long time, this is often true. But if you’re trying to do difficult things, things which are not known to be possible, it is not true. The more difficult your mission, the more details there will be that are critical to understand for success. You might hope that these surprising details are irrelevant to your mission, but not so. Some of them will end up being key. Wood’s tendency to warp means it’s more accurate to trace a cut than to calculate its length and angle. The possibility of superheating liquids means it’s important to use a packed bed when boiling liquids in industrial processes lest your process be highly inefficient and unpredictable. The massive difference in weight between a rocket full of fuel and an empty one means that a reusable rocket can’t hover if it can’t throttle down to a very small fraction of its original thrust, which in turn means it must plan its trajectory very precisely to achieve 0 velocity at exactly the moment it reaches the ground. Some important details for colonizing the universe. You might also hope that the important details will be obvious when you run into them, but not so. Such details aren’t automatically visible, even when you’re directly running up against them. Things can just seem messy and noisy instead. ‘Spirit’ thermometers, made using brandy and other liquors, were in common use in the early days of thermometry. They were even considered as a potential standard fluid for thermometers. It wasn’t until the careful work of Swiss physicist Jean-André De Luc in the 18th century that physicists realized that alcohol thermometers are highly nonlinear and highly variable depending on concentration, which is in turn hard to measure. You’ve probably also had experiences where you were trying to do something and growing increasingly frustrated because it wasn’t working, and then finally, after some time you realize that your solution method can’t possibly work. Another way to see that noticing the right details is hard, is that different people end up noticing different details. My brother and I once built a set of stairs for the garage with my dad, and we ran into the problem of determining where to cut the long boards so they lie at the correct angle. After struggling with the problem for a while (and I do mean struggling, a 16’ long board is heavy), we got to arguing. I remembered from trig that we could figure out angle so I wanted to go dig up my textbook and think about it. My dad said, ‘no, no, no, let’s just trace it’, insisting that we could figure out how to do it. I kept arguing because I thought I was right. I felt really annoyed with him and he was annoyed with me. In retrospect, I think I saw the fundamental difficulty in what we were doing and I don’t think he appreciated it (look at the stairs picture and see if you can figure it out), he just heard ‘let’s draw some diagrams and compute the angle’ and didn’t think that was the solution, and if he had appreciated the thing that I saw I think he would have been more open to drawing some diagrams. But at the same time, he also understood that diagrams and math don’t account for the shape of the wood, which I did not appreciate. If we had been able to get these points across, we could have come to consensus. Drawing a diagram was probably a good idea, but computing the angle was probably not. Instead we stayed annoyed at each other for the next 3 hours. Before you’ve noticed important details they are, of course, basically invisible. It’s hard to put your attention on them because you don’t even know what you’re looking for. But after you see them they quickly become so integrated into your intuitive models of the world that they become essentially transparent. Do you remember the insights that were crucial in learning to ride a bike or drive? How about the details and insights you have that led you to be good at the things you’re good at? This means it’s really easy to get stuck. Stuck in your current way of seeing and thinking about things. Frames are made out of the details that seem important to you. The important details you haven’t noticed are invisible to you, and the details you have noticed seem completely obvious and you see right through them. This all makes makes it difficult to imagine how you could be missing something important. That’s why if you ask an anti-climate change person (or a climate scientist) “what could convince you you were wrong?” you’ll likely get back an answer like “if it turned out all the data on my side was faked” or some other extremely strong requirement for evidence rather than “I would start doubting if I noticed numerous important mistakes in the details my side’s data and my colleagues didn’t want to talk about it”. The second case is much more likely than the first, but you’ll never see it if you’re not paying close attention. If you’re trying to do impossible things, this effect should chill you to your bones. It means you could be intellectually stuck right at this very moment, with the evidence right in front of your face and you just can’t see it. This problem is not easy to fix, but it’s not impossible either. I’ve mostly fixed it for myself. The direction for improvement is clear: seek detail you would not normally notice about the world. When you go for a walk, notice the unexpected detail in a flower or what the seams in the road imply about how the road was built. When you talk to someone who is smart but just seems so wrong, figure out what details seem important to them and why. In your work, notice how that meeting actually wouldn’t have accomplished much if Sarah hadn’t pointed out that one thing. As you learn, notice which details actually change how you think. If you wish to not get stuck, seek to perceive what you have not yet perceived.
Ray Bradbury once explained with a poem why he writes science fiction and why space travel is so important to him. It is perhaps my favorite poem. Text version: The fence we walked between the years We ached and almost touched that stuff; O, Thomas, will a Race one day stand really tall Short man, Large dream I love this poem deeply for how dumb his reason is. He’s very straightforward about why he dreams of space travel ‘Twould teach us, not to, never to, be dead Advancing space travel is a silly way of try to escape death, but when the mind really really wants something, it clings to the best plan it can find for achieving it. Even if that plan is very very dumb. I see a lot of honor in this poem because while many hope to escape death, few are willing to admit to themselves, much less talk openly about their dumb plan for it. Their friends and family would think they were foolish, naive and a bit suspect – only villains want to cheat death. But Bradbury was willing to dream openly anyway. His courage makes it easier for us to have courage too. I have a similar awed respect for the child who whispers quietly to herself when she’s alone ‘I wish mom wouldn’t hit me’. They both have the virtue of looking directly at a terrible darkness they are powerless in front of and whispering ‘I wish that weren’t there’. The poem is also tragic now that he’s dead. It reminds me of all those who have gone before me, longing futilely and silently, and now he has joined them. My mother and the many billions of other humans who preceeded me. And hoped by stretching tall that they might keep their land I, too, long to keep my soul.
More in science
How do you tell friend from foe in a split second? These beautifully designed WWII guides used silhouettes and vehicle details into a system for recognizing tanks, planes, and ships on sight.
Regular readers may recall that I put a visit to Tulainyo Lake on my bucket list a few years ago. Last week I did it. Impossibly remote, otherworldly beauty, and an enduring mystery. Just how deep was this lake? Wikipedia claims not to know. Measuring it is non-trivial. A worthy challenge. The skinny: This relatively small alpine lake is about 117 m deep! That makes it the 25th deepest natural lake in North America, and by far the deepest lake on Earth for its size. Enjoy our interactive report here.
[Note that this article is a transcript of the video embedded above.] I love the periodic table of the elements. I love it because it reveals the deeper order of what seems like an otherwise wildly disparate collection of atoms with different physical forms, chemical properties, and nuclear stabilities. I love it because, even before we actually found the elements that fit into each box, we knew that something did and could even predict some things about those elements before they were ever discovered. And finally, I love it because it’s a bit messy. Not everything lines up perfectly, and in some ways, it’s still a work in progress. In many ways, human-created standards follow that same form, and I want to try and convince you that they deserve the same affection. Let me present the periodic table of standard North American electrical connections. Isn’t it beautiful? I’m fascinated by stuff like this: a diversity of needs and purposes put into a relatively nice, neat order. But why do we need so many? And where do any of these actually get used? Well, I’ve spent the past month reading just about everything I could find on electrical plugs and receptacles to figure those questions out, and I even have a few of them here so I can show you what I learned. I’m Grady, and this is Practical Engineering. Electricity is something we really don’t want to be proprietary. It’s one thing if your charger doesn’t work on your buddy’s cell phone. It’s another thing entirely when you have to rewire your house because you bought a different brand of toaster. The National Electrical Manufacturers Association, or NEMA, was founded in 1926 as a coalition of companies making electrical equipment. Their members realized that life would be better with some standards, so that any company making an electrical device could be reasonably confident that the people who might want to buy that device would be able to use it, and more importantly, use it safely. This didn’t happen overnight. It took a diverse group of manufacturers, engineers, and testing labs to form a consensus around the system we use today. And it’s far from a perfect system. My friends Mehdi and Alec have covered receptacle-related topics on their channels, including the merits and disadvantages of the NEMA designs. But it works pretty well. Well enough that the NEMA connector standards have been adopted not just in the US, but all of North America, Central America, parts of South America, Japan, Taiwan, the Philippines, and beyond. Here’s that table again. You probably noticed that every type of plug and receptacle has its own special number. They seem a bit arcane at first glance, but it’s actually a handy naming scheme that’s pretty straightforward to understand. The first number is the configuration that defines the combination of voltage rating, wire count, and grounding style. These numbers are a bit arbitrary, but they kind of represent a certain class of receptacles and plugs. For example, NEMA 1 receptacles are rated for 125 volts and have just 2 poles (a hot and neutral) with no ground. The NEMA 1-15 was the classic North American outlet until the 1960s, and you still see these in older buildings. Lots of devices made today can still use them, especially low-voltage equipment like chargers, and, critically, those without external metal parts. If an energized wire inside the device comes loose and contacts the case, there’s still an insulating barrier protecting someone from being shocked. The reason NEMA 1 receptacles are mostly a thing of the past is what could happen when equipment didn’t have that protection. If a device with a metal enclosure or exposed metal parts had an energized wire come loose, that metal would be energized too. But, critically, it might not create a short circuit. With nowhere for current to flow, the device could just sit there, indefinitely dangerous, until someone happened to touch it, allowing current to flow through them to a lower potential. The ground wire we see in nearly all plugs and receptacles today fixes that specific hazard. Bonding exposed conductive elements and connecting them to ground makes sure that if they somehow become energized, current will flow, a short circuit will form, and protective devices like breakers will activate. Today we use the NEMA 5 standard for the vast majority of receptacles and plugs. Even if you’ve never heard of NEMA or seen the other plugs on the periodic table, you’re almost certainly familiar with this design. They have a 125 volt rating to handle the standard 120 volt service for most electrical devices with a little buffer. They have an energized pole, called the hot; a neutral pole to provide a return path, and a separate ground return that is bonded to the neutral line in the main electrical panel. The ground pin on most outlets is round instead of flat, and that’s the reason why nearly all electrical outlets kind of look like they’re screaming. Or at least they do to me. One thing about NEMA 5, and actually most of the NEMA configurations, is that the outlets have polarity. On the NEMA 5-15, the neutral slot is a bit wider than the hot, making it so the plug can only go in one way. In function, polarity often doesn’t matter for AC circuits. Current travels in both directions, so the equipment inside the device can’t really tell the difference. And some devices, like switch-mode power supplies, don’t care which direction they’re plugged in. Both blades are the same size. For safety, though, a lot of devices do. You really don’t want heating elements, motor coils, and circuit boards energized and waiting for a ground. It’s less hazardous to put the switch on the hot wire so that nothing beyond the cord is energized until it’s turned on. Enforcing polarity at the plug prevents “switched neutrals” along with other issues like electrical noise. The NEMA 5-15 plug and outlet were designed to be backward compatible with the older 1-15 standard. 1-15 plugs work just fine in the modern 5-15 outlets, and there are quite a few interesting compatibility cases like that in the NEMA standards. For example, the “15” in 5-15 refers to the current rating. Nearly every household device and appliance that runs on 120 volts is designed so that it never draws more than 15 amps, and actually, if the device is meant to run for more than 3 hours continuously, like a space heater, it can only draw 80% of that (which is 12 amps if you’re keeping score at home). That limit is obviously fine for most household appliances. But, especially in commercial spaces, it’s not quite enough power for certain devices like kitchen mixers, treadmills, copy machines, and power tools. Of course, we could just change the codes to require 20-amp circuits everywhere, but that has huge implications: larger circuit breakers, heavier-gauge wiring, and more expensive receptacles. And in many cases, it’s just not necessary. So instead, NEMA created a different receptacle and plug for 120-volt, 20-amp circuits, the 5-20. I have a bunch of these in the studio. You can see they have that T shape on the neutral slot. And 20-amp devices have the neutral blade rotated 90 degrees on the plug. But here’s the backward compatibility: regular 15-amp plugs fit into the 5-20 receptacle as well. NEMA 5 has 30 and 50 amp receptacles too, although they aren’t used very often these days because of a quirk about the historic availability of voltage. Today, split phase electrical service is basically standard for residential power. You get two 120-volt hot lines which can be used individually for smaller circuits or combined to get 240-volts for circuits that need more oomph. In the early 20th century, 240-volt service wasn’t always available, so you have these very-high-current 120-volt receptacles that could power heavy commercial cleaning equipment like floor burnishers and blowers, kitchen equipment like warming cabinets and steam tables, and large shop tools like table saws and compressors. Also, not all portable generators run at 240-volts, so older models used the larger NEMA 5 receptacles as well. These are still available and installed in places where, for whatever reason, a higher-voltage circuit is hard to come by. But in most cases, the more power-hungry devices are going to run on 240-volts. That brings us to NEMA 2. Like NEMA 1, these are ungrounded receptacles, but instead of a hot and neutral, they have two hots. Each is 180 degrees out of phase with its neighbor, so you get 240-volts across them, handled with a little cushion by the 250-volt rating. There were 20 and 30 amp receptacles, but, also like NEMA 1, these are mostly obsolete now that a ground is required by code. They’ve been replaced with NEMA 6, which has 15, 20, 30, and 50-amp receptacles and plugs. Of course, with double the voltage, you also get double the power compared to the NEMA 5 equivalents at the same current rating. The 6-15 is common for window or wall-mounted air conditioners. The 6-20 is used for heavier-duty air conditioners plus commercial kitchen equipment and shop tools. The 6-30 is used with large heaters, kilns, and heavy power tools. The 6-50 is kind of the standard welder outlet, plus it’s pretty common these days for level 2 EV chargers, capable of delivering nearly 10 kilowatts of continuous power through the receptacle. Like NEMA 5, the NEMA 6 has some backward compatibility, allowing 6-15 plugs to fit into 6-20 receptacles. This is kind of clever, but it doesn’t work all the way up the different current ratings. Of course a 50-amp outlet could easily handle a 15-amp device. And it would certainly be possible to design a series of outlets where each successive jump in current rating allowed those smaller devices to plug in. But there are two main reasons why they don’t: One is practicality. The blades on plugs aren’t all the same thickness. Designing a single receptacle slot that can safely grip both a thin, 15-amp blade and a massive 50-amp one would make manufacturing more difficult and increase the chances of developing loose connections inside the receptacle over time. Two is safety: circuit breakers are sized to protect everything downstream, including the plug and the appliance cord. If a thin cord on a low-current device develops an internal short, the resistance of that thin wire itself will cap the fault current so that a larger breaker might take much longer to trip or not trip at all. That could allow the wire to reach high enough temperatures to start a fire. Of course you don’t want a high-current device plugged into a lower-current-rated circuit, but if you trace out the things that can go wrong, it turns out that you also don’t want lower-current devices plugged into a high-capacity circuit. So, the plugs and outlets are designed to prevent both cases, except for the 15 and 20 amp situation, where the current is close enough that a breaker should still work as intended. 240 volts are useful to supply more power at the same current rating, but of course it comes at a cost. Higher voltage means more potential, literally, for arcs to occur. Equipment designed to handle the higher voltage needs better insulation and more careful design. Take a clothes dryer for example. You want the extra voltage for the power-hungry heating elements, but all the other stuff inside (like timers, controllers, and clocks) can easily run on 120 and those lower-voltage components are more affordable. That’s where NEMA 10 came in. You get three poles: two hots and a neutral. In that way, you get dual voltage: 240 between the hots and 120 between each hot and neutral. Of course, NEMA 10 receptacles also lack a ground connection, so they’re mostly obsolete. Plenty of houses still have them installed for clothes dryers and kitchen ranges, but since the 1990s, they’ve been supplanted with the NEMA 14 configuration. This is the most widely-used 240-volt standard in North America today. It’s versatile, providing both voltages. And there are a full range of current capacities, allowing you to design a circuit that’s well-suited for a device, from 15 all the way up to 60 amps. The 14-15 is pretty rare. I couldn’t even find someone making the receptacle. The 14-20 is also not that common. Some food service equipment uses this like certain coffee makers. The warmers rely on 240 volts while the fans and timers run on 120. Same with some jobsite heaters and specialized laboratory equipment. The 14-30 is the standard residential electric clothes dryer plug and is often used for EV chargers. Some server and mainframe equipment uses it as well. The 14-50 is the standard residential cooking range and oven plug. It’s also widely used for EV chargers and pretty common at RV campgrounds as well. The 14-60 is more of a commercial or industrial receptacle, used for large kitchen appliances and distribution of power at events like concerts. Single phase electrical service covers nearly all residential and lots of commercial buildings. But, the grid runs on three phases and it’s pretty common for larger commercial buildings and essentially all industrial facilities to have three-phase service. It’s particularly useful for devices that use large motors. And of course, if you have the service, you’re going to need receptacles and plugs for those devices, or at least the ones that aren’t hard-wired. NEMA 11 was the standard for up to 250V with receptacles and plugs ranging from 15 to 50 amps. Those have been replaced by the new NEMA 15, again because of grounding requirements. And this is going to almost always be relatively specialized industrial devices: woodshop and machining tools, laboratory testing equipment, grinders, pumps, dust collectors, heavy welders, plasma cutters, and so on. It’s not stuff most people see in everyday life, and in many cases, each receptacle is going to be custom-installed for a specific piece of equipment. And since hard-wiring equipment directly to the service panel is typically the default, that makes receptacles like these even more rare. You really only see them in places that need a high degree of modularity, allowing for rapid reconfiguration of workspaces like jobsites, certain manufacturing facilities, and short life-cycle equipment that needs to be easily swapped out. There are two main three-phase service classes used in most commercial and industrial buildings in the US. The most common is 208 volts phase to phase, which uses the NEMA 15 configuration. There’s also 480 volts phase to phase, but like I mentioned before, you can get a lower voltage between phase and neutral (in this case, 277 volts). So NEMA 7 has plugs and receptacles specifically for using just one phase from buildings wired with 480-volt, three-phase service. A lot of commercial and industrial lights use these receptacles, like warehouses, factories, and arenas, making them easy to swap out without hard-wiring. Commercial ventilation and air conditioning systems use them too. And just like the dual-voltage 240-volt plugs, there are also dual-voltage three-phase plugs, delivering equipment with all three hot phases plus a neutral so different components can run at different voltages. NEMA 18 has receptacles for 208-volt service, although they don’t have a ground, so they’re mostly obsolete. There are no straight-blade plugs that have replaced NEMA 18. Aligning and inserting a 5-blade plug would be tricky and take a lot of force. And I’ve kind of buried the lede here only talking about the straight-blade NEMA standards. The reality is that a large number of the NEMA receptacles and plugs have an equivalent locking version. These use curved blades that twist inside the receptacle so they can’t be easily pulled out. Actually the locking versions are more common than the straight-blade equivalents in many cases, especially when it comes to portable generators, jobsite equipment, and events where things are always moving around. If your vacuum cleaner unplugs itself because you’ve gone too far into the hallway, that’s usually not a big deal, but if a three-phase 600 volt plasma cutter does the same thing, you can get serious damage from arcing. That’s why the locking standards extend beyond the voltage ratings of the straight-blade ones up to three-phase 600-volt circuits. They even have receptacles for 400-hertz power used in aerospace, submarine, and military systems. Of course, sometimes the standards make themselves. When it comes to RVs and travel trailers, (from what I can gather) the industry had already developed a 120-volt, 30-amp receptacle before NEMA formalized its catalogue of standards. Instead of forcing an entire industry to retool, NEMA just adopted what everyone was already using, calling it the TT-30. TT for travel trailer and 30 for the current capacity. In function, it’s not any different than the NEMA 5-30 receptacle and plug, but you’ll almost never see one of those, because the TT-30 is far more common. It’s a face only an outlet enthusiast could love. I haven’t really talked about the smaller versions of the locking connectors used where space is an issue. And there are even more specialized standards like ship-to-shore power, aircraft, and military uses. Of course, when you look beyond NEMA, there are way more standards out there. But I feel like this is enough to get you excited about the weird, wide world of electrical receptacle standardization. There are all kinds of practical considerations that make it much more complicated than just a 2D chart with voltage on one side and current on the other. Just like the periodic table of the elements, the NEMA connection standards are a bit messy. And that’s what I love about them.
The course of history is affected by many things, including the political and social situations of large groups of people, […]
Rethinking the electric field Have you ever wondered what an electric field actually is? The electric field is the foundation of most technologies that we rely on every day. From power grids and electronic devices to radio communication and the … Continue reading →
