extension cord
An electrical cord with a plug one end, and a single socket or a multi-port socket at the other end, used for powering one or more devices at a distance, too far from the wall outlet to be reached by the normal cords of the device or devices.
extension cord: temporary reach for electrical power
An extension cord is a flexible cable terminated with a male plug on one end and one or more female receptacles on the other, designed to deliver mains power to equipment located beyond the reach of a device's built-in cord. The basic single-outlet version consists of a length of insulated copper conductors (typically 12 or 14 AWG for general use) housed in a PVC or rubber jacket, with a grounded three-prong plug and a matching socket.
Extension cords come in standardized lengths: 25, 50, 100, and 150 feet are common, though shorter 6 to 12 foot versions dominate workshop and indoor use. Multi-outlet power strips extend this principle further, offering 4 to 8 receptacles in a single unit. Heavy industrial applications use 10 or 8 AWG cable for longer runs or higher amperage equipment. Voltage ratings vary: household cords handle 120V; industrial versions may run 240V or 277V. Always match the cord's amperage rating to the equipment: a 13-amp cord feeding a 15-amp tool will overheat and create fire risk.
Voltage drop and distance
A critical limitation of extension cords is voltage drop across long runs. A 150-foot cord carrying a 15-amp load can drop 10 to 15 volts from supply to outlet, starving motors of rated power and generating heat in the conductor itself. This is why manufacturers specify maximum recommended lengths for different gauges and loads: a 14 AWG cord should not exceed 50 feet at full amperage; a 12 AWG can run 100 feet. Exceeding these limits dims lights, weakens tool performance, and risks cord failure.
Failure modes include insulation degradation from UV exposure (outdoor cords must be marked SOOW or equivalent), crushing under equipment wheels, and water ingress in damp environments. The cord's jacket can crack, exposing live conductors. Poor connections at either end create arcing and resistance heat. Undersized cords in long runs suffer internal overheating independent of ambient temperature. Outdoor-rated cords with thicker jackets and UV stabilizers cost more but survive weather and wear.
In industrial settings, extension cords are a temporary expedient, not infrastructure. Fixed wiring, panels, and properly positioned outlets are the proper solution for permanent workstations. Temporary cords must be inspected before each use: check for cuts, burns, water exposure, and loose connections. Some sites ban daisy-chaining multiple cords together, as each joint introduces resistance and failure risk. The term itself reflects their intended role: an extension of existing service, not a replacement.