Features
Power cables may be either fixed or detachable from the appliance. In the case of detachable leads, the appliance end of the power cord has a socket rather than a plug to link it to the appliance, to avoid the dangers from having a live protruding pin. Cords may also have twist-locking features, or other attachments to prevent accidental disconnection at one or both ends. A cord set may include accessories such as fuses for overcurrent protection, a pilot lamp to indicate voltage is present, or a leakage current detector. Power cords for sensitive instruments, or audio/video equipment may also include a shield over the power conductors to minimize electromagnetic interference.
A power cord may have a retaining clamp, a mechanical device that prevents an appliance coupler from inadvertently being pulled or shaken loose. Typical application areas with stricter safety requirements include medical technology, stage and lighting technology, and computing equipment. For specialty equipment such as construction machinery, sound and lighting equipment, emergency medical defibrillators and electrical power tools, used in locations without a convenient power source, extension cords are used to carry the electrical current up to hundreds of feet away from an outlet.
In North America, the National Electrical Manufacturers Association develops standards for electrical plugs and receptacles and cables.
International power cords and plug adapters are used in conjunction with electrical appliances in countries different from those in which they were designed to operate. Besides a cord with one end compatible to receptacles or a device from one country and the other end compatible with receptacles or devices from another country, a voltage converter is usually necessary, as well, to protect travelers' electronic devices, such as laptops, from the differing voltages between the United States and places like Europe or Africa.
North American lamp cords have two single-insulated conductors designed for low-current applications. The insulator covering one of the conductors is ribbed (parallel to wire) for the entire length of the cord, while the other conductor's insulator is smooth. The smooth one is hot and the ribbed one is neutral.
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—Robert Frost (1874–1963)
“Each reader discovers for himself that, with respect to the simpler features of nature, succeeding poets have done little else than copy his similes.”
—Henry David Thoreau (1817–1862)
“These, then, will be some of the features of democracy ... it will be, in all likelihood, an agreeable, lawless, particolored commonwealth, dealing with all alike on a footing of equality, whether they be really equal or not.”
—Plato (c. 427–347 B.C.)