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

Practical Electricity And House Wiring

Of course modern wiring methods will not permit the use of this kind of switch, so we will actually use one of those shown in Fig. 13, which does exactly what the knife switch does, except that all parts carrying electricity are carefully concealed and the action is very quick. The complete circuit with this switch is shown in Fig. 25.

Tracing Circuits.—For convenience in following the arrows which indicate the flow of electricity, the wire from the Line to any lamp will be shown as a dark, heavy line which will be referred to as a "black" wire; the wire from the lamp back to the Line will be shown as a light line, which we will call the "white" wire. If the lamp is to be coati oiled by a switch, that portion of the black wire from the switch to the lamp will be shown as a dark, heavy dotted line. In this way it will be easier to trace the circuits in a uniform way. You will find it easiest to assume that electricity flows in on the black wire, out on the white.

If now you will go back to our comparison with water in pipes, and imagine that the lamp is for example a water motor through which water must flow for it to turn, and that wires are pipes through which the water flows to the water motors (lamps), these circuits will be very clear if you will follow the arrows which indicate the course of the water (electricity). If the valves (switches) are turned on, water (electricity) will flow through the water motors and they will turn (the lamps will light) ; when the valves (switches) are off, nothing will happen.

So far we have discussed only one lamp on a circuit; we now want to light three or more. Most beginners make the mistake of wiring them as shown in Fig. 26, which is known as wiring "in series."

Lamps "in Series."—Let us analyze why this is not practical. Let us assume that each lamp is of a different size; then let us go back to our comparison with the water motors. Suppose the first requires one gallon of water per minute to operate, the second three gallons, and the third five gallons. So far as the lamps are concerned, one may require 1 ampere to operate, one 3 amperes, one 5 amperes. If they are all in "series" (as this style of wiring is known) the amount of water or electricity that can pass through any of the three is limited by the size of the smallest one: if the smallest one permits only one gallon per minute, or one ampere, to pass, obviously this is not enough to operate the largest.