Electric cords, or power supply cords, consist of a conducting medium, typically copper, an insulating material, and an outer protective jacket. Power supply cords are usually permanently affixed to a piece of equipment or appliance and are used in fields such as sound and lighting equipment, retail appliances, electrical power tools, and for many personal appliance uses.
Power supply cords vary in length according to intended use and application, but in cases where a longer cord is required, extension cords would be more likely to be used. Typically power supply cords are flexible, although they can be semi-rigid, and have an electrical plug at one end that is used to connect to a wall socket.
The configurations of the plug and socket need to match as the successful transfer of energy is dependent upon the tight fit between the corresponding prongs of the electrical plug and the openings of the socket, or electrical receptacle. The size of the cord wire is determined by the amount of voltage that is required to flow through the cord. Cord wire sizes and current carrying capacities are designated in accordance with the American Wire Gauge standards.
As with any component used in the transfer of electrical energy, there are safety precautions to take into consideration. Personal injury, death, and/or property damage can occur as a result of the deterioration, malfunction, or misuse of electrical equipment, including power supply cords.
When determining the appropriate electric cord for an application, electric cord manufacturers adhere to specifications concerning voltage rating, current, length, wire size, protective materials, as well as plug configuration.
The National Electrical Manufacturers Association (NEMA) determines the standards in North America for plug and power cord production, and other countries with their own testing standards and voltage capabilities set and adhere to their own standards. Manufacturing standards help to maintain consistency within the field of power cord production and decrease the chances of malfunctions due to quality standards.
Polarization of an electric plug at the end of a power supply cord ensures that the equipment is connected to the neutral, or grounded, side of the circuit, and reduces the risk of potential electric shock to those handling the equipment. This is an important manufacturing consideration and sensitive electrical equipment and products should only be used with polarized or grounded power supply cords.