There are hundreds of different kinds of power cords, and they vary according to their function as well as the country in which they are used. However, in the U.S., power cords fall into three basic categories and are distinguished by the kind of appliance they are used with and the safety features they have. These three kinds are: ungrounded cords, grounded cords, and appliance-specific cords.
This is the most basic kind of power cord. It has a two-prong connector at each end and a thin plastic covering over the wires. The advantages to this kind of cord are that it can fit in any wall socket, (including two-prong sockets found in some older buildings), and that it is unobtrusive because of its size. Its disadvantages are in safety. Because it has no grounding wire, a metal-encased appliance may become electrified, or "hot," in the event of a short circuit, (whereas a grounded cord would send this electricity to the circuit breaker and trip it). Additionally, because it lacks a metallic shield or thick plastic sheath, it may give off electromagnetic radiation and heat, particularly when carrying a large current. Nonetheless, these kinds of cords are inexpensive and work well for lamps and other small appliances.
A grounded cable varies from an ungrounded cable in several important ways. First, it has a three-prong connector at each end, with the third prong connected to a grounded wire. If a metal-encased appliance short circuits, the electricity will flow through the grounded wire and trip the circuit breaker. Typically, grounded power cords also have a thick plastic sheath to contain heat. They will also sometimes have a metallic shield to contain electromagnetic radiation. This kind of cord is generally more expensive and more obtrusive than an ungrounded cable, but it is much safer when using metal-encased appliances, including computers and other electronics that have a metal-encased power supply even though there is a plastic covering over it.
These cords come with appliances, everything from coffee makers to computers. On one end they have a two or three-prong connector which is plugged into the wall, and at the other end they are either permanently connected to the appliance, or have a female plug. Typically these cords are modeled after either the ungrounded or grounded cords described above, depending on what kind of appliance they are being used for. Common kitchen appliances will generally have two-prong plugs, whereas electronics, studio lights and other large appliances will generally have three-prong plugs.
There are many, many words for power cords. Often these have to do with distinguishing between different types of cords, but other times the same kind of cord will have a different name in a different context. On a film or television set, for example, a "cable" is a heavily insulated, grounded cord that is designed to carry a large current, while a "stinger" is a common grounded or ungrounded extension cord. In many contexts, a power cord that has a common connector on each end is referred to as a "cord set." Other common names for power cords are "power cable" and "mains lead."
Countries Other Than the U.S.
In foreign countries there are many different plug configurations and often the power supply is different from that in the U.S. However, the basic principles described above hold true for these plugs as well.
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