It is necessary to know how cords are wired when working on any electrical project. Round and flat cords look different; however, they are wired the same.
Standard Wire Color Coding
Color coding for wires inside cords is standard throughout a country, and knowing the color codes is necessary for any electrical wiring work. In the United States, the three main colors inside a cord are black, white and green. Black is always the hot wire, white is always the neutral, and green is always the ground. In the United Kingdom, the hot wire is always brown, neutral is blue, and the ground is green with a yellow stripe.
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Two-Wire Flat Cords
Flat cords that have only two wires, such as those used in most lamps, are not marked by colors. The hot wire is always smooth on the outside of the cord, while the neutral wire is ribbed on the outside. For flat cords with polarized plugs on the end, the larger prong (or terminal) is the neutral wire.
Three-Wire Flat Cords
Three-wire flat cords contain a smooth (hot) wire, a ribbed (neutral) wire and a green (ground) wire. If there is a male plug on the end, the green wire will connect to the round pin, the smooth to the smaller prong and the ribbed to the polarized larger prong. The ground pin ensures that the cord is plugged in correctly.