Remember a few years back when there was the story about the little girl who did an "Alexa, order me a dollhouse" on the news and people watching the show had their Alexas pick up on it and order dollhouses during the broadcast? Wait until there's a widely watched Netflix show where someone says "Delete C:\Windows".
My wake word is "Computer" like in Star Trek, so I'm really worried I'll be rewatching an old episode and it'll kill the electrical grid when someone says "Computer, reverse the polarity."
(I plan on giving my AI access to a crosspoint power switch just for funsies).
You know I've been meaning to ask somebody, people always make a fuss about which is which but like.. schuko and europlug and a few others are omnidirectional and aren't even labelled so chances are stuff is always plugged in wrong and it all works fine. I guess it's all rectified anyway so it doesn't matter?
It does matter in some cases. For example, in Edison screw desk lamps, the tip is supposed to be connected to line, with the outer ring connected to neutral. If this is reversed, there is a risk you can shock yourself screwing or unscrewing a bulb while the lamp is turned on, because now line is on the outside, much closer to your fingers. Worse, the light switch would now be switching neutral, so even turning the lamp off won't stop this.
I mean I'm sure there are lots of cases where it's a problem, also AC motors should run backwards and the neutral will be contaminated, right?
What I'm wondering more about is how it's compensated for (some kind of AC rectifier in the plug?) when symmetrical plugs will cause this error in 50% of cases. Like were the highly regarded people writing the standards just like "fuck it, if he dies he dies"?
Most things will operate just fine with line/neutral reversal. AC motors will not run backwards; they use a phase shift capacitor [1] to ensure that they always start turning in the same direction regardless of where line is (relative to neutral) when the motor is instantaneously connected to a source of AC power.
As you say, most things run on DC, and rectifying AC to DC doesn't care about line/neutral reversal.
It does create some safety issues in certain applications as I described above.
It can cause some things to misbehave. For example, in home energy monitoring, where you clip one or more current transformers around a circuit's line conductor(s) to measure the current consumption of that circuit and connect an AC-AC transformer (to reduce it to a lower voltage, to make it suitable for export on an extra-low-voltage finger-accessible connector like a barrel plug, and so that it can be measured by an analog-to-digital converter) to the unit, so that the unit can measure voltage (and thus work out power) [2], then if line/neutral is reversed, its observation of what it thinks is line will be at the wrong point (relative to its observation of neutral) when computing the power being transferred. This will result in the device telling you that the circuit is exporting power (when it is actually importing), or vice versa.
It all depends upon the application. In most instances, line/neutral reversal is fine; and indeed with non-polarised plugs, unavoidable. However it should be avoided if possible.
"This should be avoided if possible" and "This widespread standard makes it unavoidable" sound like two things that should not inhabit the same universe lol.
I feel like the intent was that there is a chance that this might happen, and they wanted manufacturers to make sure it's always handled properly... so there's no better way to force them to do that by making it happen constantly everywhere. Given that people don't really die from this on a daily basis I presume it must've somehow worked.
The US is starting to come around in this regard (which is elaborated in the video I linked). Polarised NEMA 1-15 and 5-15 sockets are now the norm in new construction; with the neutral slot being slightly taller than line in both. It is therefore not possible to insert a polarised NEMA plug in the other way around.
The only difference between the two is that NEMA 1-15 has no ground while NEMA 5-15 does; a NEMA 1-15 plug will go into a NEMA 5-15 socket (but not the other way around). NEMA 1-15 sockets will still be common in situations that don't require a ground connection, such as sockets intended for class 2 equipment in bathrooms (like mains-powered shavers), but are now polarised, preventing line-neutral reversal when used in combination with a polarised plug.
However, there will be a significant lag time. Lots of devices are still sold with non-polarised plugs, for compatibility with both types of socket. Until non-polarised sockets go away, and electrical inspections enforce that all polarised sockets are wired correctly, and then devices are only sold with polarised plugs, appliance line/neutral reversal will still be a daily occurrence. This will take at least a couple more decades to be rid of.
There was an effort to standardise a polarised socket and plug specification for all of mainland Europe (IEC 60906-1), but this was shelved in the 1990s and abandoned in 2017 due to cost and waste concerns. IEC 60906-1 sockets appear to be unpolarised at first glance (for plugs lacking an earth pin); however, line and neutral are required to have shutters on them that only open with the insertion of a longer earth pin (just like UK BS1363 sockets), and thus you cannot insert a 2-pin plug into it in either orientation.
A lot of the rest of the world has only polarised plugs and sockets. This includes the UK, India, Malaysia, Brazil, Israel, China, and South Africa, which collectively make up just under 40% of the world's population. That list isn't exhaustive, but I can't be bothered looking up the socket standard in use by every country in the world and reading the specification for those standards to see if they permit unpolarised plugs :)
Polarized receptacles were mandated in the US by the National Electric Code in 1962. I feel like during the 1990s every electronic device you bought had a polarized plug, but then with the advent of smartphones circa 2007-2008 and then the flood of aftermarket chargers a few years later, we suddenly went backwards to non-polarized plugs.
