Sizes and Types of Wire

Wire is sized by gauge, the larger the gauge number the smaller the wire. Wiring also can be stranded or solid. Printed on the insulation layer of the wire is information pertaining to size and voltage-handling capacity.

Home Wiring

Wiring for inside the home is generally governed by electrical codes set up by the local governments, either city or county. Many home centers have code books that tell you what you need.

Rewiring Lamps and Appliances

When replacing the plug wire for a lamp or appliance simply look at the old wire and get a replacement of the same size. If the information isn't there, then look on the back or bottom of the item for the electrical information label and get wiring that meets or exceeds the specification.

Extension Cords

When choosing an extension cord you need to look at both the amount of power the item you are plugging in will draw, and the distance between the wall outlet and where you are using the item. The farther away and the larger the power draw, the larger the extension cord you need. For example: An item drawing 7 amps of power 25 feet away needs a thinner cord that a large power tool drawing 15 amps 50 or 100 feet away.

Source:

Hometips

Do-it-yourself Manual, Reader's Digest, 1974

Alabama Electrical Code, Including the 2008 National Electrical Code