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I never understood why US uses a wider pin on two prong plugs for the hot wire. Browsing the web site I got the idea that no one in the world cares about polari

by dexzod 4y ago

I never understood why US uses a wider pin on two prong plugs for the hot wire. Browsing the web site I got the idea that no one in the world cares about polarity, both pins are the same size. This is a huge usability issue for people with weak eyesight or when plugging in something in a tight area such as behind a couch or bed.

mwint 4y ago
Because there’s a bunch of legacy wiring out there that doesn’t have a ground wire, only hot/neutral. So if you’re designing an appliance that has to work with these two-prong outlets, especially if it has a metal housing, you want to know which wire is the “shock your customer” one and which is the “probably don’t shock the customer” one.
gumby 4y ago
Because often devices have their metal shell grounded, especially older lamps and radios, but also toasters and the like. Plug it in the wrong way and the metal shell is hot. Nowadays a lot of devices are made of plastic and / or are DC powered so it doesn’t matter as much.
linsomniac 4y ago
There was a time when ground pins were not common, and "double insulated" devices were not as common as today. Some of those devices grounded the chassis to the neutral in the receptacle. The only device I know that I've encountered which fit this was the oscilloscope in my high school physics lab. If you plugged it in the wrong way (which could happen but I don't recall how that was possible), and you touched the metal body of the scope, you'd get a little zap out of it.
ars 4y ago
The wider pin is on the neutral not the hot. Everyone cares about polarity - when you have a 3 prong plug, then the ground forces the orientation of hot vs neutral, and the two prongs are the same size.
- gattilorenz 4y ago
  > Everyone cares about polarity - when you have a 3 prong plug, then the ground forces the orientation of hot vs neutral, and the two prongs are the same size. EU/German/Shuko and Italian plugs are entirely reversible and grounded, that’s what the OP probably was referring to. There’s no way to force an orientation (and thus a “polarity”)
axiolite 4y ago
> This is a huge usability issue for people with weak eyesight What is it about weak eye sight that prevents someone from turning their plugs over when they find it doesn't fit the first time? Are people with weak eyesight also all THAT short of time as well? Far easier with polarized NEMA plugs than, say, USB-A. > I never understood why US uses a wider pin on two prong plugs Because single-pole switches are cheaper, and ensuring the outer contact on an Edison light bulb screw fixture is neutral and NOT energized is an important safety feature.

by dexzod 4y ago

mwint 4y ago

Because there’s a bunch of legacy wiring out there that doesn’t have a ground wire, only hot/neutral. So if you’re designing an appliance that has to work with these two-prong outlets, especially if it has a metal housing, you want to know which wire is the “shock your customer” one and which is the “probably don’t shock the customer” one.

gumby 4y ago

Because often devices have their metal shell grounded, especially older lamps and radios, but also toasters and the like. Plug it in the wrong way and the metal shell is hot. Nowadays a lot of devices are made of plastic and / or are DC powered so it doesn’t matter as much.

linsomniac 4y ago

There was a time when ground pins were not common, and "double insulated" devices were not as common as today. Some of those devices grounded the chassis to the neutral in the receptacle. The only device I know that I've encountered which fit this was the oscilloscope in my high school physics lab. If you plugged it in the wrong way (which could happen but I don't recall how that was possible), and you touched the metal body of the scope, you'd get a little zap out of it.

ars 4y ago

The wider pin is on the neutral not the hot. Everyone cares about polarity - when you have a 3 prong plug, then the ground forces the orientation of hot vs neutral, and the two prongs are the same size.

gattilorenz 4y ago
> Everyone cares about polarity - when you have a 3 prong plug, then the ground forces the orientation of hot vs neutral, and the two prongs are the same size. EU/German/Shuko and Italian plugs are entirely reversible and grounded, that’s what the OP probably was referring to. There’s no way to force an orientation (and thus a “polarity”)

axiolite 4y ago

> This is a huge usability issue for people with weak eyesight What is it about weak eye sight that prevents someone from turning their plugs over when they find it doesn't fit the first time? Are people with weak eyesight also all THAT short of time as well? Far easier with polarized NEMA plugs than, say, USB-A. > I never understood why US uses a wider pin on two prong plugs Because single-pole switches are cheaper, and ensuring the outer contact on an Edison light bulb screw fixture is neutral and NOT energized is an important safety feature.