Extension cord
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A British extension cord with a power indicator and switches for each individual socket. |
An
extension cord (also known as a
power extender, or an
extension lead, sometimes known as an
extension cable, but that has a distinct meaning from
extension cord for many people) is a length of flexible electrical
power cable (flex) with a
plug on one end and one or more sockets on the other end (usually of the same type as the plug). The term usually refers to
mains (household AC) extensions but is also used to refer to extensions for other types of cabling. If the plug and receptacle are of different types, the term "adapter cord" may be used.
Some extension cords also incorporate safety features, such as a polarized plug and receptacle,
grounded terminals, a 'power-on' indicator, a
fusible link, or even a
residual-current device (also known as a ground-fault circuit interrupter or GFCI).
Extension cords come in various lengths and thicknesses, and service duties. In general, the more power needed by the appliance, the thicker the cord should be (that is, larger
wires inside). Cords to be used outdoors, in wet areas, around oils, or exposed to sunlight for long periods should be selected for such specific service.
In the
USA where the domestic voltage is 110 V, the
National Electrical Code (NEC) prohibits the use of extension cords in a 20 A circuit unless they are of 16
AWG or larger (for example, 14 AWG or 12 AWG). As with other flexible cords, the NEC also prohibits their use where attached to building surfaces, or concealed inside walls, floors, or ceilings, above suspended ceilings, or where run through holes or other openings (windows, doors) in structures (with limited exceptions). Cords run across the floor should be covered with a suitable device to protect them from physical damage.
Other countries also regulate the use of extension cables but the specific conditions and the nature of the regulation varies. In
Europe and elsewhere where the normal domestic voltage is around 230 V, there is less risk of causing fire through overheating of cables for any given power due to the lower current. However most European extension cables now include an automatic current cut-out to avoid misuse of the cable. This requires manual re-setting if excess current is drawn through the cable. (American multiplug cords also include such a device but single- or triple-outlet cords do not.)
An extension
reel is an extension lead that rolls up, usually into the socket end, which in some cases has more than one socket on it (often 2 or 4). Another type of extension reel hangs near the plug end and permits the user to draw the cord out by grasping the socket end .
A
power cord is similar but the socket end is designed to mate with a panel plug (usually IEC or figure 8 style) and is usually much shorter. With IEC connectors cables are frequently seen with a line plug and socket. These may be considered either as powercords (if IEC outlets are in use) or as extensions (if used to extend a powercord.
Extension cords may sometimes refer to cables that transmit data, electricity, or both (for example,
USB extension cable). This type of cable comes in handy when certain USB plugs cannot fit into the hubs, such as a
USB flash drive. But they are more likely to be called "extenders" or "extender cables" or "cable extenders".
A
power strip is a block on the end of a power cable with a number of
sockets (usually 3 or more), often arranged in a line. This term is also used to refer to the whole unit of a short extension cord terminating in a power strip.
*
Domestic AC power plugs and sockets*
retractable
