Equipment such as construction machinery, sound and lighting equipment, emergency medical defibrillators, and electrical power tools are often used in locations without a convenient power source, and extension cords are thus used to supply the current to the equipment.
There are many different types of extension cords, ranging in capacity from light household to heavy-duty industrial, and they are constructed by encasing conducting wire, usually copper, of differing gauges in a rubber protective jacket. The wires are responsible for conducting electrical voltage from a wall socket to the electrical appliance.
One end of the extension cord will hold an electrical plug, otherwise known as male. The prongs on the electrical plug fit into the corresponding holes in the wall socket, or electrical receptacle, thus providing a connection to allow the flow of electrical energy from the power source, through the extension cord and to the appliance. The optimum flow of energy through the extension cord depends on a tight fit between the socket and the plug.
Cord length, wire gauge, and cord operating distance are all important factors to consider when choosing extension cords. The capability of an extension cord to successfully handle the required flow of electrical energy will depend on these factors and the quality of electricity transmitted will be affected accordingly.
The National Electrical Manufacturers Association (NEMA) is responsible for setting the standards used in North America for electrical supply components, and this ensures a high quality of electrical supply is maintained.
As with any component used in the transportation of electrical energy, there are important safety precautions to be considered. Personal injury, death, and/or extensive property damage could occur as a result of the deterioration or misuse of electrical power supply equipment, including extension cords. Extension cords are only designed for temporary usage, and not as a means of permanent or long-term power supply.
Polarized sockets and plugs are used in an attempt to minimize some of the potential dangers of using extension cords by implementing a connection to a ground wire. Circuit breakers and fuses can also be used in extension cords, serving to cut off electrical energy flow in the case of a power surge or overheating.