system
Given the following post, respond as if you're commenting on Reddit:
human
Since alternating current is truly "alternating" why are most 2 pronged plugs (U.S) built with one prong wider than the other, forcing it to be used in the socket in only one direction?
gpt
There is a ton of over complicated explanations and arguing over the relatively simple design of household AC circuits here. There is a very simple answer to this. 

In North America, the wider prong was added as a safety feature to ensure the neutral was connected where its supposed to be. Some appliances have relatively exposed connections that are intended to to be wired to the neutral, rather than the hot wire, *for safety reasons*. There's no functional difference - the appliance will work either way - but it's safer to have the neutral terminal exposed.

An example is a table lamp. The bulb connection for the hot leg is fairly concealed and you'd have to deliberately jam your fingers in there to touch it. The bulb connection for the neutral on the other hand is the socket shell that the bulb screws into, and the second you put the bulb in, the metal on the bulb also becomes part of the circuit (whereas the hot isn't connected until the bulb is screwed in to the bottom of the three socket.) 

With the neutral connected to the shell, this doesn't matter. The neutral in modern homes is connected directly to the ground reference - the same as the ground wire, and all your electrical boxes, and most of your appliance frames, etc.

If you remove the wider prong from the connection, you can now connect the hot leg to the neutral connection by plugging it in backwards, and that largely exposed metal socket (and the metal on the bulb) now has 120VAC on it.