Incandescent lamps are available in hundreds of different bulb shapes with a wide range of light output, energy consumption, and life ratings. Energy consumption can range from a fraction of a watt for a flashlight lamp to more than 10,000 W for a floodlight.

The number and types of available incandescent lamps are astonishing. Typical manufacturers' catalogs list hundreds of different bulb styles with a wide range of wattage and voltage ratings, estimated useful lives, output in lumens, and other special qualities. However, average hardware stores, home improvement centers, and supermarkets narrow the number and type of lamps they carry down to the relatively few of those that are most familiar and most likely to be purchased by consumers.

The smallest incandescent lamps are made for flashlights, holiday lighting strings, and instruments, while the largest bulbs, with diameters exceeding 20 in., are spotlights and street lights. Mid-sized incandescent lamps, typically rated from 40 to 200 W, are those most widely used in home and office lighting.

All incandescent lamps are made in essentially the same way, and today these processes are automated. Figure 8-1 shows the construction of a typical incandescent lamp. The filament leads are encased in glass and mounted on a glass stem assembly with a glass exhaust tube. The blown glass bulb, which has been coated inside or "frosted," is then sealed to the stem in a machine. Gas flames directed at the mating edges of the glass parts melt them to form...