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North American plugs and sockets

Standard power sockets

Rating: 15A 125V

These are two standard NEMA 5-15R sockets, as found in most installations in North America. The vast majority of them are duplex receptacles, that is, they have two outlets, and mount to a rectangular wall box using two screws on the top and bottom.

The faceplate has two semi-round cutouts for the two sockets, and is held with a single, fairly short screw. More recently, "Decora" sockets using a rectangular style of cover plate have also become common, especially in newer installations.

Notably, once the faceplate is removed, it's very easy to touch the live screws on the side, as they aren't recessed behind plastic. Care must be taken, then, to make sure the screw has been fully tightened when installing the faceplate.

Wiring these outlets can be done in one of two ways: the best, and recommended, method is to use the screws to the side. The wire is bent in a circular shape using some pliers, and is then placed around the screw which is then tightened, forming a good connection. There are also side tabs present which can be removed to wire the two outlets independently, for example to use one with a light switch.

The second, and worse, method is to use the push-in slots ("back-stabs") present on the back, which take less time to use but offer a considerably worse connection, and are thus discouraged. Some higher-end outlets use rising clamp terminals like on European sockets, but this isn't common on standard ones.

Standard types of plug

North American plugs have two flat blades for line and neutral, as well as a round earth pin, on earthed plugs. The non-earthed plugs are known as NEMA 1-15P, and can be either polarised or non-polarised; polarisation (that is, being able to distinguish between line and neutral) is achieved by having a slightly larger neutral slot, which then only allows the plug to fit in one way. Earthed plugs (NEMA 5-15P) are always polarised, and thus generally use pins of the same width.

One major flaw about the American plugs is their completely unsleeved pins, which make it easy to get an electric shock when the plug is partially inserted.

Tamper-resistant (TR) outlet

Rating: 15A 125V

In the last few years, sockets with safety shutters have become mandatory for new and renovated installations. These outlets, which are referred to as "tamper resistant" (TR), work and are built the same as normal ones, but they have shutters, which only open when two pins of a plug are pushing into them. This helps prevent people from sticking metal objects into a socket and receiving an electric shock.

Adoption is at the moment somewhat slow, as these are only really found in newer installations and non-TR sockets are still found in the majority of houses, can still often be bought at hardware stores, and aren't required (and thus generally never found) on things like power strips and extension cords.

GFCI-protected outlet

Rating: 15A 125V (20A feed-through)

This GFCI-protected power outlet, commonly referred to just as "a GFCI", features built-in protection against leakage currents. A GFCI (or RCD in Europe) protects people from shocks by detecting a difference between line and neutral. If this exceeds a certain amount, in this case 5mA, the device trips and disconnects the power.

Compared to Europe, in North America it's generally only common to see this form of protection in "wet" areas such as bathrooms and kitchens. Additionally, it's almost always found in the sockets themselves, rather than on the breaker panel.

This device features two outlets (with shutters) for connecting devices, as well as "load" terminals to hook up other sockets, which will also be protected. "Test" and "reset" buttons are present on the front, for testing the correct operation of the GFCI and turning the power back on when it has tripped.

20A power socket

Rating: 20A 125V

These outlets (NEMA 5-20R) are used with 20A circuits, and allow for connection of standard 15A plugs as well as 20A plugs.

While 20A circuits have become more common in American homes, 15A sockets are still the ones most commonly installed, as using them on 20A circuits is allowed and there are very few appliances aside from special use cases that actually use 20A plugs.

Old bakelite 2-prong plug

Rating: 15A 125V

This is an old 2-prong (unearthed) NEMA 1-15P plug, made of two identical piece of bakelite to save cost. As common with old plugs of this style, it's not polarised, which means it can be inserted in either direction.

It's interesting to note that this plug was actually made in Italy, though the UL and CSA markings indicate that it was clearly meant for the export market.

Vintage unpolarised three-way adaptor

This is a very simple three-way adaptor, which enables the use of three appliances on a single socket. In particular, this is a non-earthed one, and also unpolarised, due to its age. Unpolarised sockets like on this device are somewhat useless nowadays, as many non-earthed devices now have a polarised plug. However, it could still be used with certain items such as phone chargers.

Old connector sockets with 3 outlets

Rating: 15A 125V

These are two vintage connector sockets built by Leviton and Eagle, for use at the end of an extension cord. Both of them are made of bakelite and have three non-polarised outlets on them, which is definitely indicative of their age.

A screw on the front is present, which can be removed to reveal the wire connections inside. While rewireable ones like these have definitely become uncommon, it's still possible to buy extension cords nowadays with something similar to this at the end, though obviously modern ones use polarised outlets and have a slightly different look.

Ground defeater adaptors

These adaptors convert a 2-prong outlet into a three-prong one, with a tab meant to the used for the earth connection. In theory, this is supposed to only be used with a 1-15P socket in a grounded wall box: the tab would connect to the screw holding the faceplate and thus would make it possile to connect earthed devices safely

However, in practice, these are almost always just used to bypass the earth connection entirely, in houses that lack 3-prong outlets. It's a very well known practice, with the "official" purpose of these adaptors likely being just an excuse to continue to legally sell them.

Lamp socket adaptors

Rating: max 660W

These adaptors connect to a normal lampholder and convert it to two 2-prong power outlets, to plug in standard electrical appliances in situations where an outlet may otherwise not be available. They also feature a pass-through lamp socket for a lightbulb, and the newer one also has a pull-cord to switch it on or off.

Devices like these were often used in the early days of electricity all around the world, as it was mainly used for lighting back then and thus very few power sockets were generally present in a room. While in Europe these haven't been made since the 50s/60s, American equivalents continue to be made nowadays, and they're still sometimes used for special applications.

There are also simpler versions of these adaptors, which only feature one outlet and are thus much smaller. Notably, all of these adaptors have a very small power rating (660W), understandable since a lamp socket isn't meant to handle a large amount of current, but there's no fuse or breaker to actually enforce this.

Note: the older items shown at the end are both unpolarised, and are made by Leviton and General Electric.