The wires which the young experimenter is likely to use in his work the most are known as magnet wires, and are used for making electro-magnets, coils, and various windings. Magnet wires may be insulated with either silk, cotton, or enamel.
Silk-covered and cotton-covered wires may be obtained with either a single or double covering.
Wires with a single covering of silk or enamel are used when it is desirable to save space, for the covering of these two classes of magnet wires is thinner than either the cotton or double-silk-covered wire, and consequently they require less room for winding.
The size of the wire is indicated by its diameter, and in the United States is measured by the Brown and Sharpe gauge, often indicated by the term, "B. & S."
The preceding table shows the various sizes of wire of the Brown and Sharpe gauge, and also several of their characteristics, such as weight, resistance, etc.
Insulators
The covering placed over wires is not the only precaution taken to insulate them, but in the case of permanent wiring they are usually mounted on glass or porcelain supports.
Fig. 89.—Staples and Wooden Cleat used for running Low Voltage Wires.