ElectricCuriousityFilter
March 16, 2025 1:29 AM Subscribe
Why do electric outlets outside the US have switches? I’ve seen this in Spain, Portugal, Australia, and New Zealand so I expect it’s pretty common globally. Like, if I plug something into an outlet presumably I want power to go to it. Asking because sometimes the switch is close enough to the outlet that it blocks my big global power adapter.
I’d guess at two things:
1. Safety - if the switch is off, then your toddler can poke a knife into the socket without surprises
2. Convenience - sometimes you want something off, but want it to stay in situ, and it’s better to leave the plug in the socket than on the floor (especially with UK plugs)
posted by Mostly Harmless at 1:42 AM on March 16
1. Safety - if the switch is off, then your toddler can poke a knife into the socket without surprises
2. Convenience - sometimes you want something off, but want it to stay in situ, and it’s better to leave the plug in the socket than on the floor (especially with UK plugs)
posted by Mostly Harmless at 1:42 AM on March 16
Best answer: Unplugging an appliance that is on is more likely to produce an arc the higher the voltage is, so a switch is more important on a 230v outlet than a 110v one.
Your question made me curious so I read the relevant bits of AS 3000 and AS/NZS 3112, which govern this in Australia. They are quite clear that switching is mandatory but don't give much more than an oblique reference to arcing as a hint at the reason. It is my best guess, the standards don't really worry much about convenience but do mandate switches.
posted by deadwax at 2:53 AM on March 16 [6 favorites]
Your question made me curious so I read the relevant bits of AS 3000 and AS/NZS 3112, which govern this in Australia. They are quite clear that switching is mandatory but don't give much more than an oblique reference to arcing as a hint at the reason. It is my best guess, the standards don't really worry much about convenience but do mandate switches.
posted by deadwax at 2:53 AM on March 16 [6 favorites]
UK mefite here: I like using socket switches as a quick way of ensuring all appliances plugged into a particular socket are turned off (or on). I could unplug everything- but that would be a little messier. The switches always work in the same way and are often marked with red on top to visually indicate the circuit is live. The actual switch design makes or breaks contact cleanly and is safer than removing a plug in marginal conditions (wet hands for example). Electrical appliances are safer these days - but the practice of going through all the sockets in a kitchen, workshop or office - to ensure everything was turned off before leaving - is a useful option. Finally- if you have an appliance you DONT want people to turn off accidentally- then you can put some tape over a switch to discourage it.
posted by rongorongo at 2:54 AM on March 16 [3 favorites]
posted by rongorongo at 2:54 AM on March 16 [3 favorites]
Further to Mostly Harmless' post, in the UK we have a 3-pronged plug where the top prong (earth) is slightly longer than the line (live) and neutral prongs.
Aside from the safety benefits of earth being touched first when putting the plug in and last when taking it out (basically it's very hard to get an electric shock if the appliance is properly earthed) it also operates the line and neutral shutters in many modern sockets These shutters stop little hands poking something metal in to the socket and getting a shock. But not every socket has the shutters (and they're not impenetrable anyway) so every socket must have a switch which cuts power to the socket as well. So yes, 100% a safety feature. There are also other benefits mentioned by others here but it is first and foremost a safety feature.
(for anyone with a nerdy interest in electrical safety here is a copy of the British Standards BS 1363 - 13A plugs, socket-outlets, adaptors, and connection units PDF that details all of the requirements. It's not the very latest copy, I don’t think, but you have to pay for the latest copy and it's recent enough to give you the general idea of current UK safety standards)
posted by underclocked at 3:20 AM on March 16 [3 favorites]
Aside from the safety benefits of earth being touched first when putting the plug in and last when taking it out (basically it's very hard to get an electric shock if the appliance is properly earthed) it also operates the line and neutral shutters in many modern sockets These shutters stop little hands poking something metal in to the socket and getting a shock. But not every socket has the shutters (and they're not impenetrable anyway) so every socket must have a switch which cuts power to the socket as well. So yes, 100% a safety feature. There are also other benefits mentioned by others here but it is first and foremost a safety feature.
(for anyone with a nerdy interest in electrical safety here is a copy of the British Standards BS 1363 - 13A plugs, socket-outlets, adaptors, and connection units PDF that details all of the requirements. It's not the very latest copy, I don’t think, but you have to pay for the latest copy and it's recent enough to give you the general idea of current UK safety standards)
posted by underclocked at 3:20 AM on March 16 [3 favorites]
Best answer: It's optional for UK sockets. The regulations say that there must be some way to switch off the appliance in emergencies, but that can mean unplugging it or turning it off at the consumer unit. Unswitched sockets are pretty rare nowadays, and I don't know an electrician who'd fit one unless asked to. I have an aquarium with around a dozen different plugs going into a couple of extensions, and every socket in the extension has a switch. It's handy when I need to turn off two or three things off during a water change, as having those switches is a lot easier than unplugging/re-plugging them all.
posted by pipeski at 4:23 AM on March 16
posted by pipeski at 4:23 AM on March 16
Because of quirks of history, UK outlets have a heck of a lot more oomph available. A ring circuit might be able to provide 240V (nominally 230V) at 32A, though individual plugs are usually fused for 13A. That's roughly four times the power of a US 115/15A socket. Shoving a fork in that would be quite the show. It's important to be able to disable power safely and cleanly.
posted by Rhomboid at 4:32 AM on March 16 [3 favorites]
posted by Rhomboid at 4:32 AM on March 16 [3 favorites]
The US is not really an anomaly here - sockets do not have switches in much of Central Europe all of which is on 230V. It’d be interesting to see statistics of how frequently these events that switches are trying to prevent are in different geographies.
posted by koahiatamadl at 4:45 AM on March 16 [4 favorites]
posted by koahiatamadl at 4:45 AM on March 16 [4 favorites]
Statistics on how often switches would have prevented accidents would be interesting and my guess is that they aren't really necessary or central Europe would adopt them. There's a surprising amount of someone thinking a rule was necessary in 1928 and now it's part of local orthodoxy, to the point of being in law, contained in electrical regulations, despite them being thought of as empirical. Have a look at the British rules around power in bathrooms, which persist despite the long-standing lack of any problems in places without them.
That all said, switches are very convenient.
posted by deadwax at 4:59 AM on March 16 [4 favorites]
That all said, switches are very convenient.
posted by deadwax at 4:59 AM on March 16 [4 favorites]
Best answer: I think this goes back to the history of DC and AC power generation.
Unlike the US which largely switched over to AC power in 1890 the UK stuck to DC power in many cities up until around 1960, the last disconnection was in 1981.
At 240V DC, you can get a nasty electrical arc when you withdraw a plug from a socket, though many were actually 180v to 220v, each city had its own standards. This was before the introduction of the current 3-pin UK plugs (we had a variety of round pin plugs in different sizes). To make this safer, they put a switch on the socket: turn off the socket and then pull the plug. If there was any arcing it would be inside the socket away from your hand.
So although changes have been made from DC to AC, voltage levels and a completely different and much safer plug/socket design, the use of switches on the outlet has become a UK norm that everyone now expects.
posted by Lanark at 5:50 AM on March 16 [1 favorite]
Unlike the US which largely switched over to AC power in 1890 the UK stuck to DC power in many cities up until around 1960, the last disconnection was in 1981.
At 240V DC, you can get a nasty electrical arc when you withdraw a plug from a socket, though many were actually 180v to 220v, each city had its own standards. This was before the introduction of the current 3-pin UK plugs (we had a variety of round pin plugs in different sizes). To make this safer, they put a switch on the socket: turn off the socket and then pull the plug. If there was any arcing it would be inside the socket away from your hand.
So although changes have been made from DC to AC, voltage levels and a completely different and much safer plug/socket design, the use of switches on the outlet has become a UK norm that everyone now expects.
posted by Lanark at 5:50 AM on March 16 [1 favorite]
Best answer: Something less known about Lord Reith - is that, as well as being the first Director General of the BBC he also chaired the "Electrical Installations Committe" which worked between 1941 and 1945 to define better electrical standards for post-war deployment to the empire - and which churned out the first edition of BS1363 -upon which the country's domestic electrical system is based. Reith was an minister's son by upbringing and an engineer by training - so I like to think it was his influence that - just like with with radio presenters who had to wear dinner jackers under his command - the unwashed masses were going to get infrastructure which was best for them -even if 99% of us might never notice or understood why it was built that way. So: blame him for the plug sockets, for better or worse.
posted by rongorongo at 6:06 AM on March 16 [2 favorites]
posted by rongorongo at 6:06 AM on March 16 [2 favorites]
240V mains electricity demands respect.
When I was a tiny Australian child, I was taught to always, always, make sure the switch was off before plugging in or unplugging an electrical cord. Which makes sense if the risk being mitigated is arcing where plug meets socket, though that risk was never actually articulated as far as I recall.
At the time, standard Australian plugs didn't have the half-length insulating sleeve on the pins that they do now, so I guess there could have been some possibility that a small child's finger could slip down between plug and socket and touch a live contact as a plug was being removed from an unswitched outlet.
The other thing that was just kind of in the air as the normal thing to do when I was a kid was switch off any appliance at the wall socket before leaving it unattended even if the appliance had its own switch, and make sure all appliances were switched off "completely" - meaning at the wall - before leaving the house. Again, it was never really explained why this was good, but everybody knew that it was.
I was seventeen years old when I first experienced real gratitude for having had this practice drilled in for so many years, returning home from school one day to find the cat on the kitchen bench having a good old chew on the cloth-and-rubber-covered cord for the electric kettle. He'd managed to expose quite a lot of bare copper.
posted by flabdablet at 6:12 AM on March 16 [5 favorites]
When I was a tiny Australian child, I was taught to always, always, make sure the switch was off before plugging in or unplugging an electrical cord. Which makes sense if the risk being mitigated is arcing where plug meets socket, though that risk was never actually articulated as far as I recall.
At the time, standard Australian plugs didn't have the half-length insulating sleeve on the pins that they do now, so I guess there could have been some possibility that a small child's finger could slip down between plug and socket and touch a live contact as a plug was being removed from an unswitched outlet.
The other thing that was just kind of in the air as the normal thing to do when I was a kid was switch off any appliance at the wall socket before leaving it unattended even if the appliance had its own switch, and make sure all appliances were switched off "completely" - meaning at the wall - before leaving the house. Again, it was never really explained why this was good, but everybody knew that it was.
I was seventeen years old when I first experienced real gratitude for having had this practice drilled in for so many years, returning home from school one day to find the cat on the kitchen bench having a good old chew on the cloth-and-rubber-covered cord for the electric kettle. He'd managed to expose quite a lot of bare copper.
posted by flabdablet at 6:12 AM on March 16 [5 favorites]
Most of the Schuko-countries (blue in this map) as well as Belgium, France, Switzerland and Italy don't generally have switched outlets. Denmark has them on 107-2-D1 sockets, not on Schuko AFAIK. And similar to BS1363, Schuko makes safety ground first, breaks last, and the recessed socket makes it as good as impossible to touch the live and neutral pins when they touch the socket contacts.
posted by Stoneshop at 8:41 AM on March 16 [1 favorite]
posted by Stoneshop at 8:41 AM on March 16 [1 favorite]
Response by poster: Thanks all, lots of goood answers. Especially the imposing Lord Reith.
posted by billsaysthis at 10:32 PM on March 16
posted by billsaysthis at 10:32 PM on March 16
if I plug something into an outlet presumably I want power to go to it.
And when you don't?
For things like wall warts, you have to either unplug them when not in use, or just put up with the wasted power.
Being able to switch things off is much more convenient.
Also some appliances still suck significant power when 'off'. With a switch on the socket, there's no doubt.
posted by HiroProtagonist at 9:44 PM on March 17
And when you don't?
For things like wall warts, you have to either unplug them when not in use, or just put up with the wasted power.
Being able to switch things off is much more convenient.
Also some appliances still suck significant power when 'off'. With a switch on the socket, there's no doubt.
posted by HiroProtagonist at 9:44 PM on March 17
poster: Thanks all, lots of goood answers. Especially the imposing Lord Reith.
One other person who you might be interested in regarding the forming of modern British electrical standards, is Caroline Haslett - who played a key role on The Electrical Installations Committee. She was a former suffragette who had trained as an engineer in the First World War. She was particularly focused on using engineering to free up women from “domestic drudgery”, she had practical experience of wiring her own flat back in the 20s and then of working to improve the safety and effectiveness of kitchen appliances. By WW2, the standards committee was looking ahead to a world with such wonders as home laundry machines and even televisions. So - under her influence- there appears to be a feminist aspect to your answer: women in that era were going to experience the results of good or bad domestic electrical design disproportionately. They - or the children they were raising- were going to get electrocuted if things weren’t safe. They were the ones who would be working with kettles, washing machines, vacuum cleaners- most of the time. Given all that perspective: of course there should be fuses in plugs, of course the plugs should have a safety first design and of course the sockets should have a switch on them!
posted by rongorongo at 11:33 PM on March 18 [1 favorite]
One other person who you might be interested in regarding the forming of modern British electrical standards, is Caroline Haslett - who played a key role on The Electrical Installations Committee. She was a former suffragette who had trained as an engineer in the First World War. She was particularly focused on using engineering to free up women from “domestic drudgery”, she had practical experience of wiring her own flat back in the 20s and then of working to improve the safety and effectiveness of kitchen appliances. By WW2, the standards committee was looking ahead to a world with such wonders as home laundry machines and even televisions. So - under her influence- there appears to be a feminist aspect to your answer: women in that era were going to experience the results of good or bad domestic electrical design disproportionately. They - or the children they were raising- were going to get electrocuted if things weren’t safe. They were the ones who would be working with kettles, washing machines, vacuum cleaners- most of the time. Given all that perspective: of course there should be fuses in plugs, of course the plugs should have a safety first design and of course the sockets should have a switch on them!
posted by rongorongo at 11:33 PM on March 18 [1 favorite]
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It seems to be one of those American Exceptions we keep hearing about.
posted by unearthed at 1:40 AM on March 16 [4 favorites]