In 1906, the newly established International Electrotechnical Commission developed a set of 13 standards for electric sockets or inlets, matching each with specific power cords, connectors and cables. Each standard consists of a power connector referred to as "female," matched with a "male" socket or inlet conforming to the IEC 60320 specification. Each type has a matching appliance rating based on amperage, as well as class rating, depending on whether it has a grounding connector or not.
C2 and C4
With similar IEC standards, the C2 and C4 sockets have two round conductors and no earth or grounding conductor. An earth conductor -- the third conductor in a socket or electrical plug -- redirects or dissipates excess electric current to avoid voltage overloading. A socket with an earth conductor rates as a class 1 inlet; a socket without a conductor is a class 2 inlet.
The difference between the C2 and C4 is in the appliance coupler rating, where the C2 registers up to 0.2 amperes and the C4 to 2.5 amperes. Appliance coupler rating refers to the maximum electric current the socket and power cable bring to an appliance. Both sockets commonly appear in small electronic devices and appliances, such as electric razors and clippers.
The C6 socket, a class 1 socket due to its earth conductor, is a three-conductor inlet. The male conductors are round and the appliance coupler rating is 2.5 amperes. It has one top round connector, which serves as the ground, and two round connectors beneath, making it look like a cloverleaf. The C5 connector -- the standard match for this socket -- normally appears in notebook and laptop power supplies.
The C8 socket acts like the C4 but looks different. The C4 sports a top half-square appearance, while the C8 has an inward curve at the top and bottom part of its centre -- the space between the two conductors. The C8 matches with a C7 connector in power supplies for portable electronic devices such as laptops and video-gaming consoles.
The C10 ranks as the first IEC socket featuring a vertical and rectangular conductor. Partnered with a C9 connector, the C10 socket is a class 2 inlet with a 6-ampere appliance coupler rating. The squarish socket's normally used for traditional 220V appliances, such as TVs and electric fans.
C14 and C16
The C14 and C16 sockets -- commonly found in desktop computers, heavy-duty IT equipment and kitchen appliances -- have two primary rectangular conductors topped with a rectangular earth conductor above them, making them class 2 inlets. With an appliance coupler rating set at 10 amperes, the C14 socket has a maximum temperature rating of 70 degrees Celsius, while the C16's rated at 120C, for appliances such as electric kettles and pressure cookers. The C16 socket and its matching C15 connector are the standard used in Australia. In the U.K., the standard C16A variant has a maximum temperature rating of 155C.
While similar to the C14 and C16 and found on most of the same appliances, the C18 lacks an earth conductor. However, as most newer appliances consist of grounding conductors, finding an appliance with a C18 socket may be difficult.
The C20 class 1 socket sports horizontal, rectangular conductors often used in Europe for computer and IT-based devices. It maintains the same appliance ampere and temperature rating as the C14.
The C22 socket's a mix of the C14 and C20 sockets, with the same three-conductor configuration as the C14, but laid out horizontally like the C20. This socket has an appliance coupler rating of 16 amperes and a maximum temperature rating of 155C. Some European countries use this socket as the standard for household appliances.
A rarely used standard, the C24 features the same conductor set-up as the C20 socket, but without the earth conductor. It also maintains the same maximum temperature and ampere rating as the C20 socket.
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