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I live in Europe, but have a 110V electric toothbrush charger that lives in my suitcase. Every US hotel I visit, this plugs in to the bathroom 110V socket just as one might expect.

In Europe in hotels there is often a 110V socket offered as well as a 220V socket. I often forget to bring my European charger with me, and try to use the US one in the 110V socket. This appears to be designed to take flat pinned plugs as well as round pin ones (a typical example is here - the top answer here has a similar picture), but 99% of the time I can't insert the US plug into the socket, despite pushing quite hard.

I wondered if this was a quirk of my toothbrush charger (Oral B). So out of interest I tried inserting other US 110V plugs (not using them, because the current available is small) including Apple power supplies, and they don't fit either. I've also had problems inserting Apple power supplies (they don't care about voltage) into "universal" sockets in hotel bedrooms - I think I have only ever got this to work in 110V "dedicated" sockets in airport hotels in Europe.

Am I misunderstanding the point of 110V "shaver" sockets in European hotels? Are they not to allow our US friends to plug in their US shavers / toothbrush chargers? Do I need some weird 110V to 110V adaptor? (Yes, I know the obvious answer is not to forget my European charger)

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    Almost all modern US plugs will have one blade wider than the other (neutral is wider).
    – Jon Custer
    Dec 27, 2023 at 22:13
  • @JonCuster they do indeed. But why would non-US 110V sockets not accept "almost all modern US plugs" (if that is what you are suggesting)? Though clearly this permits a route where I take a file to my plugs ...
    – abligh
    Dec 27, 2023 at 22:25
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    Because they are designed to only accept shavers. I assume US shavers have plugs with identical blades. Dec 28, 2023 at 6:38
  • So the toothbrush was bought in the US, and is double insulated, so you would have thought would be the same. I will admit I don't have a US shaver.
    – abligh
    Dec 28, 2023 at 7:38
  • I have experienced this in reverse. On an early trip to the US, I expected to be able to use my UK toothbrush charger as it accepted 110V and had a 2 pin plug. It would not fit in the US hotel sockets. US electrics do not differ only in voltage from the rest of the world.
    – badjohn
    Dec 28, 2023 at 9:05

1 Answer 1

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The “US-style” ungrounded plugs (NEMA 1-15, with two flat prongs) come in two varieties: the older unpolarised (with two identical prongs) and the more recent polarised version with one of the prongs slightly wider than the other (one is neutral and the other is hot/live).

Standard NEMA receptacles (1-15 in rare cases but most frequently 5-15, with a third prong for ground) are polarised and will accept both.

Shaver supply units will usually only accept the unpolarised version.

Normally AC adapters (so-called “chargers”) don’t need a polarised plug (as evidenced by the fact that their Europlug counterparts do not have any polarity), but it seems that nowadays in the US many have the polarised version of the plug anyway, and won’t fit into shaver supply units.

You may be able to find polarised-to-unpolarised adapters, but it’s a lot easier to use a travel adapter which will do the same, though one may wonder if it’s really advisable in a bathroom.

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  • I take it the isolation transformer in a shaver supply socket makes it "incorrect" to accept polarised plugs (because neither terminal is neutral)? This just makes me confused as to why US provided double-insulated chargers (eg for toothbrushes) have polarised plugs anyway. I suspect the solution is either "dremel" or me to buy a 230V charger than also lives in my luggage.
    – abligh
    Dec 28, 2023 at 22:26
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    @abligh the Wikipedia section on the subject says that in the US they dropped the transformers in shaver sockets in favour of GFCI, which I guess keeps the polarity and means unpolarised sockets are extremely rare in the US, so everybody uses polarised plugs even though they’re useless in this case…
    – jcaron
    Dec 28, 2023 at 23:23

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