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Light bulbs.

Article Excerpt
There are three main types of light bulbs: incandescent, fluorescent and high-intensity discharge (HID). Generally, the higher the wattage, the greater the light output.

Bulb Finishes

Originally, only clear glass was used to make incandescent bulbs, which left the bright filament exposed and resulted in a harsh, glaring light. To remedy this, special finishes are used to reduce the glare by diffusing the light.

Clear glass is still used in applications where accurate light control is desired and in decorative lighting.

A frosted finish used to he the most common. Light loss averages less than 0.5 percent due to the frosted finish.

Today, light diffusion is usually accomplished by applying a coating of fine powder to the inside surface of the bulb. This coating provides a softer, more even distribution of light and reduces glare. Inside-coated bulbs are made in colors as well as white. A variety of colors are available in outside coated bulbs which can be either transparent or translucent.

Bulbs can be made to direct the light by applying a reflecting material to the inside surface of the bulb, or in the ease of R, PAR and sealed beam, light can also be directed by beveled cuts on the surface of the bulb.

General Classes of Light Bulbs

Bulbs come in a variety of shapes, sizes and designs, each with a different purpose. Bulb shapes have letter codes that correspond to a general guideline. For example, "C" refers to cone-shaped bulbs and "T" to tubular bulbs.

General service is the Type A (arbitrary) bulb used for lower-wattage bulbs from about 15 watts to 200 watts. This type is normally used for home lighting.

Vibration service is used on machinery or where continuous vibration could cause early failure of the filament. These bulbs have lower lighting efficiency.

Rough service bulbs withstand shocks and bumps. The relatively long filament is securely mounted with many supports but has a lower efficiency than general and vibration service bulbs. They are used in workshops and garages and with trouble lights.

Appliance bulbs are for ovens, refrigerators, freezers, microwave ovens and range hoods.

Special coated bulbs are covered with a Teflon[TM] or silicon protective material to prevent shattering and to resist breakage upon contact with water. They are recommended for use in trouble lights and out door fixtures.

Decorative bulbs with clear or coated flame-shaped glass, smooth B type glass, Cline glass with bent tip bulbs and globe-shaped bulbs are useful in chandeliers and wall bracket fixtures where fashion is important.

Reflector[R] bulbs are usually, made of "soft" glass tot indoor service as a directional light source with a built-in reflector. These are available as spot or floodlights.

Projector (PAR) bulbs are made of hard heat-resistant glass molded into a reflector and lens that are sealed together. Most are weather-resistant.

Elliptical reflector bulbs are shaped differently than the parabolic reflector bulbs, bringing light to a focus a couple of inches in front of the bulb. Less light is wasted in deep-baffle fixtures, and glare is reduced in downlight fixtures.

Light Bulb Bases

Light bulbs come with a variety of bases...