In electrical sockets, why is one slot larger than the other?

Answer 1

The polarization of electrical plugs is for safety reasons. The larger prong is the 'ground' side, while the smaller prong is the 'hot' side. For 2-prong plugs (without the 3rd safety ground), the polarized plug helps to guarantee that the appliance is connected properly. That is, the ground side of the 120 volt is properly connected to any internal chassis or metal inside the appliance.

Some appliances and tools are double-insulated and do not require a polarized plug. Appliances that are not double-insulated may have possible exposed metal that under a fault condition may expose the user to the metal (and hence a shock). A polarized plug ensures that the exposed metal is connected to the 'ground' side of the AC circuit.
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Answer 2

This is valid in US and countries which use the same standard. This is to distinguish between the two wires coming to the socket; one is "live", the other is "null". The null is connected to the ground, and thus offers some protection. For better protection, you need a separate wire which is connected only to the ground (the round hole in the middle)

Answer 3

The socket was designed that way to idiot proof its' use. (Poka Yoke) Some elecrtical devices need to be plugged in a certain way and therefore they designed a way to make it impossible to plug them in backwards.

Answer 4

AC actually has a "polarity" to it.
One is considered "high" and the other is considered "low" (the bottom roundish one is ground of course)

Answer 5

To keep the electrons from spilling out on to the floor. I hate it when that happens. nm

Answer 6

So you know which way to put the plug in!