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A power socket is a device to which electrical devices can be connected to receive the electric current required for their operation. Connected by a system of cables to a power source, usually an electricity generation facility operated by an energy production company, it generally has no moving parts. Instead, it contains metal strips which make contact with the prongs of an electric plug inserted into the socket. It’s through these contacts that the electric current is transmitted.
Electrical devices which connect to a power source through a power socket are considered to be portable because they can easily be connected and disconnected from the power source. Portable electric devices have a length of cable terminating in a two-, three- or four-prong plug. The prongs are shaped like blades or cylinders, and may be a combination of the two. When a plug is inserted into a power socket, a circuit is completed. Every power socket thus needs at least two slots — one with a live or “hot” contact strip to transmit current to the device being plugged in, and one to return the current.
Most modern plug and socket combinations are configured so that the plug will fit into the socket only one way. This ensures that the current is transmitted to the device only through a single hot wire. Standard power sockets for most electrical devices worldwide contain two or three slots — the third slot is for grounding, a safety feature that diverts current in the event of a short-circuit in the device. Some contain a fourth slot; this slot is for an additional hot wire for devices requiring double the standard voltage.
A Ground Fault Interruptor (GFI) is a special type of power socket. Unlike other sockets, which simply provide connection points for portable electric devices, a GFI can detect leakages of current and interrupt the circuit quickly enough to prevent injury. These sockets are frequently installed in kitchens and bathrooms, where the outlets, and the devices they power, are close to water sources. GFI outlets are frequently installed outdoors in protected receptacles as well.
Residential construction is most commonly equipped with power sockets in duplex configuration; that is, they have two sets of slots and can accommodate two plugs. Customizing power sockets to accommodate more plugs is an easy task for most electricians, though, and some configurations have four, six or more outlets. In most cases, all such outlets are powered by the same source, but it’s possible to wire each outlet separately. The most common such application is called switched outlets, in which some outlets are wired to wall switches, which control the power to those outlets and the devices plugged into them.
Electricity follows the same laws around the world, but power sockets vary to accommodate regional standards. In North America, for example, most portable electrical devices are built to operate on an electric current of 60 hertz (Hz) delivered at 120 volts. Four-slot sockets carry a second hot wire, doubling the voltage to 240 volts. This standard is also observed in parts of South America and Japan.
The European standard, which is followed by most of the rest of the world, delivers current of 50 Hz at 230 volts. Devices built to meet this standard have plugs which will not fit into the North American power outlets. Generally, these plugs have short cylindrical metal rods which are inserted into corresponding round holes in the power outlets. There’s a wide range of socket and plug combinations accommodating the European standard, in some cases with projections on the socket designed to fit into female slots in the plug.
The different voltage and current standards worldwide, as well as the many different types of power sockets and plugs, create problems and confusion for travelers. In some cases, it’s possible to purchase adapters to interconnect various combinations of plugs and sockets. Frequently, though, voltage converters are necessary to achieve compatibility with local power standards.