Editing AC power plugs and sockets (section)

== Safety features ==
{{More citations needed section|date=May 2021}}

=== Protection from accidental contact ===
Designs of plugs and sockets have gradually developed to reduce the risk of electric shock and fire. Plugs are shaped to prevent bodily contact with live parts. Sockets may be recessed and plugs designed to fit closely within the recess to reduce risk of a user contacting the live pins. Contact pins may be sheathed with insulation over part of their length, so as to reduce exposure of energized metal during insertion or removal of the plug. Sockets may have automatic shutters to stop foreign objects from being inserted into energized contacts.<ref name="ReferenceA">{{cite book |title=The History of Electric Wiring |author=John Mellanby |date=1957 |publisher=Macdonald |place=London}}</ref> Sockets are often set into a surround which prevents accidental contact with the live wires in the wall behind it. Some also have an integrated cover (e.g. a hinged flap) covering the socket itself when not in use, or a switch to turn off the socket.

=== Overcurrent protection ===
Some plugs, particularly the British ones, have a built-in [[Fuse (electrical)|fuse]] which breaks the circuit if too much current is passed.

=== Earthing (grounding) ===
A third contact for a connection to [[Ground (electricity)|earth]] is intended to protect against insulation failure of the connected device. Some early unearthed plug and socket types were revised to include an earthing pin or phased out in favour of earthed types. The plug is often designed so that the earth ground contact connects before the energized circuit contacts. The assigned IEC [[appliance classes|appliance class]] is governed by the requirement for earthing or equivalent protection. Class&nbsp;I equipment requires an earth contact in the plug and socket, while Class&nbsp;II equipment is unearthed and protects the user with [[Appliance classes#Class II|double insulation]].

{{anchor|Polarization}}

=== Polarisation ===
Where a "[[Ground and neutral|neutral]]" conductor exists in supply wiring, polarisation of the plug can improve safety by preserving the distinction in the equipment. For example, appliances may ensure that switches interrupt the live side of the circuit, or can connect the shell of a screw-base lampholder to neutral to reduce electric shock hazard. In some designs, polarised plugs cannot be mated with non-polarised sockets. In most [[NEMA connector#NEMA 1|NEMA&nbsp;1]] plugs, for example, the neutral blade is slightly wider than the hot blade, so it can only be inserted one way. Wiring systems where both circuit conductors have a significant potential with respect to earth do not benefit from polarised plugs.

=== Voltage rating of plugs and power cords ===
[[File:NEMA Plug Ratings.jpg|thumb|Ratings of NEMA&nbsp;5-15 (type&nbsp;B) plug marked on the label (left: 7&nbsp;A 125&nbsp;V), engagement face, and [[IEC 60320]] C13&nbsp;connector at the appliance end of the cord (centre, right: both 10&nbsp;A 125&nbsp;V)]]

Plugs and [[power cord]]s have a rated voltage and current assigned to them by the manufacturer. Using a plug or power cord that is inappropriate for the load may be a safety hazard. For example, high-current equipment can cause a fire when plugged into an extension cord with a current rating lower than necessary. Sometimes the cords used to plug in dual voltage 120&nbsp;V / 240&nbsp;V equipment are rated only for 125&nbsp;V, so care must be taken by travellers to use only cords with an appropriate voltage rating.
{{clear}}