The Golden State: Where & How to Live, Secure, Visit, Enjoy and Thrive in California

Practical Electricity And House Wiring

If you have difficulty anywhere, fall back on the water-and-pipe idea; trace the electricity in on the black wire; if you can trace it through the switch, through the lamp, back through the white wire to the Line, the lamp will light when you turn on the switch controlling it. The wire may not be laid out in the shortest line, but the circuit will work and it is then just a matter of common sense in actual wiring to run the wires so that the least amount of materials will be used.

Wires And Insulation

Many different kinds of wire are used in electrical work, each serving its own purpose. It is a relatively simple subject to understand if we give it a little study, and it is equally easy to recognize the different kinds if we study their construction and purpose.

Sizes of Wire.—Before analyzing the different kinds, let us give a little time to sizes of wire. The smaller the number, the heavier and thicker the wire, as Fig. 46 shows. In house wiring No. 14 is ordinarily used, but for the main wires coming into the house, No. 8 is the minimum size permitted by the Code, and No. 6 is the size usually used.

Nos. 16 and 18 are used on cords to electrical appliances and sizes finer than No. 18 are used in manufacturing electrical devices of all kinds. No. 40* is the smallest size usually found and is so fine that there are miles of it in one pound. On the other end of the scale, for example, in wiring very large motors, wires usually are so big that the sizes have not been given numbers, but are merely rated by their cross-sectional areas in "circular-mils." A "circular-mil" is the area of a circle one-thousandth of an inch in diameter. The table on page 53 shows the diameter of various sizes of wire in thousandths of an inch, also their area in circular mils, also the number of feet per pound, all of course pertaining to un-insulated copper wire.