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Glossary of Terms
A measure of electric current flow. One ampere (amp) will flow when one volt is applied across a resistance of one ohm.
An inert gas used in incandescent and fluorescent bulbs. In incandescent light sources, argon slows evaporation of the filament.
The width of light projected by a light source. For example, a narrow beam angle is usually described as a spot, while a wider beam is described as a flood.
Refers to a bulb with a special coating to give it a color-rendering profile similar to natural daylight.
Color Rendering Index (CRI):
A lamp's ability to render an object's true colors based on a scale of 100. Any CRI rating of 80 or above is considered high and indicates that the source has good color properties. Incandescent bulbs and daylight have a CRI of 100, the highest possible CRI. The higher the CRI of the light source, the truer it renders color.
A numerical measurement of the color appearance of a light source measured in degrees Kelvin (K). It also refers to the way color groups are perceived with "warm" colors at the red end of the spectrum and "cool" colors at the blue end.
A measure of the rate of flow of electricity, expressed in amps.
A two-terminal semiconductor through which electricity can travel in only one direction; clusters of diodes in microchip form are used in LED bulbs.
A measurement of the efficiency of a bulb, expressed in light produced (lumen) per unit of power consumed (watt).
Wire used in incandescent and halogen bulbs, usually made of tungsten and often coiled, that emits light when heated by an electrical current.
An optical device that refracts light and thus converges or diverges the beam.
A measure of luminous flux or quantity of light emitted by a source.
The gradual decline in light output from a light source over time due to filament deterioration and bulb darkening.
A measurement of how a bulb maintains its light output over time.
The light output (lumens) of a light source divided by the total power input (watts) to that source. It is expressed in lumens per watt.
A measurement of the amount of light produced by a light source. Instead of using the conventional way to choose a light source by the amount of watts or wattage, luminous flux is an alternative way of choosing the correct light source for a room or application.
A unit of light falling onto a surface that is equal to one lumen per square meter.
An inorganic chemical compound processed into a powder and deposited on the inner glass surface of fluorescent tubes, CFLs, LEDs, and some mercury and metal-halide lamp bulbs.
A measurement of energy-use efficiency--the amount of power used versus the power that is given off--that is expressed between 0 and 1, with 1 being perfect energy efficiency.
Rated Lamp Life:
The length of time of a statistically large sample of bulbs between first use and the point when 50 percent of bulbs died.
Surface-Mounted Device (SMD):
Specific style of miniature LEDs wherein the LED chip is mounted directly to the surface of a circuit board; SMDs are often referred to as the "honeycomb" LEDs.
The number of times a bulb can be turned on and off before premature light loss or the end of its life.
A measurement of the electromotive force in an electrical circuit or device expressed in volts.
A unit of electrical power. Bulbs are rated in watts to indicate the rate at which they consume energy.
Light Bulb Buying Guide
Sponsored by Bulbrite
Choose the Right Bulb for Your Lighting NeedsOne bulb is as good as another, right? Actually, no. Choosing the correct light bulb for your various fixtures can save energy, increase safety, and help create the right ambiance. But it's not always easy to select the right bulb. Use this guide to help determine the appropriate bulbs for your fixtures.
|Bulb Type Basics|
Incandescent: The incandescent bulb is the one most people are familiar with. Light is created by passing electricity to a filament and heating it until it glows a warm, white light.
Halogen: A halogen bulb is an incandescent bulb that uses halogen gas and a filament to generate light. To perform properly, the operating temperature of the bulb filament is very high and the halogen gas must be at the appropriate pressure. Quartz glass is used to protect against the increased heat.
CFL: To produce light, CFL bulbs use the interaction between mercury and other gases; the resulting glow mimics the warm, white light of incandescents.
LED: An LED bulb houses clusters of light-emitting diodes--tiny electronic chips that glow when electricity passes through them--instead of filaments or gasses.