Incandescent Lamps

This is the most familiar type of lamp. An electric current passes through and heats a tungsten filament, producing a glowing light. (The term “incandescent” literally means “to glow or become hot.”) Over time, heat evaporates the tungsten, and it eventually weakens and breaks. The lamp contains a chemically inert gas that allows the tungsten vapor from the heated element to deposit on the sides of the glass. This is why standard incandescent lamps gradually become darker over time. If they are too small, the tungsten coating would turn them opaque, and they’d be useless as a source of light. Incandescent lamps are cheap to produce and are versatile in application, but they are considered to be impractical by energy conservationists as a source of light given modern alternatives. They produce a considerable amount of waste heat for the amount of current they draw, and they have a useful life of 750 to 2,500 hours depending on the lamp. Builders traditionally install incandescent fixtures because both they and the lamps are inexpensive and are not likely to meet any resistance from price-conscious buyers. When buying lamps, take note of the voltage rating of the lamp. Typical lamps sold in stores are rated at 115 or 120 volts. At professional lighting stores, you should be able to find longer-lasting lamps rated at 130 volts.