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

Practical Electricity And House Wiring

Now it has been found that there are substances which under ordinary light appear to be innocent whitish or grayish powders. However, when these chemicals are exposed to strong ultra-violet light, they glow or fluoresce brightly —they produce visible light. Therefore, the inside surface of a fluorescent tube is simply coated with such fluorescent powder, and when the ultra-violet light created by the arc inside the tube strikes the powder, the entire inside surface of the tube glows brightly and produces the light which we see.

The advantages of fluorescent lighting are many. First of all, per watt of electricity consumed, from two to four times as much light is produced as with ordinary filament type lamps. This leads to substantial savings in power cost; it makes possible more light from a given circuit, without re-wiring (the light produced from all the fluorescent lamps a given circuit will carry, will be probably three times greater than that produced by all the filament-type lamps the same circuit will carry). In an air-conditioned building, the difference between the amount of heat produced by filament- and fluorescent-type lamps makes a substantial difference in the amount of work demanded of the air-conditioning plant. Fluorescent lamps have longer life than filament-type lamps.

Another important point in favor of the fluorescent type of lamp is the low surface brightness of the lamp; it is not bright in any one spot; the total light delivered by it is dependent not on a small area of extreme brightness, but on a large area of relatively low brightness. This results in better lighting in general, less shadows, less eyestrain, better health.

AC And DC; Single Phase And Three Phase

Direct Current.
—Fig. 268 shows what is known as a "zero center voltmeter." If you connect this voltmeter to a battery of any description, you will find that the voltmeter needle will swing, say to the right; if you reverse the wires to the batteries the needle will always swing to the left. No matter what you do to the battery or how often you try it, the needle will always swing in the same direction so long as you have the wires connected in the same way.