# Ch. 10 & 11

 The flashcards below were created by user lkillebr on FreezingBlue Flashcards. Photometry the science that measures light. Light is really visible energy. Intensity Light emitted in a specific direction by a source (luminance intensity) measured in candelas (cd) Flux light emitted in all directions by a source (luminous flux) measured in lumens Illuminance density of light at any given point on a surface. Measured in footcandles. (fc) Luminance accepted term for light that is reflected from a surfac in a given direction Exitance total quantity of light emitted, reflected, or transmitted in all directions from a surface. measured in lumens per square foot (lm/ft2) Current flow of electricity Voltage potential of flow 120/240 volt Amp (A) rate of flow, volt per second Circuit path that current flows Conductor material that allows flow Watt (W) rate of change. Volts x amp = watts Energy (kWh) amount of electrical power consumed over a period of time Cycle the interval that flow changes direction. measured in Hertz (Hz) How does a switch "break"? the flow of electricity in a circuit when it is open ("off") and it allows unimpeded flow when closed ("on") Single Pole, Single Throw Switch switch is connected at any point between the luminiare and the power supply Direct Pole, Single Throw Switch is able to direct the current to two paths at once. Three Way Switch controls an electrical load from two locations; this allows the circuit to use one of two alternate paths to complete itself Dimming systems operate on one of two principles for restricting the flow of electricity: 1) varying the voltage2) varying the length of time that the current flows during each alternating current cycle What increases the life of the lamp? Dimming incandescent sources How is the efficiency of an incandescent lamp reduced? The source is operated at less than its designed voltage because the temperature of the filament is reduced. Even though the lamps are less efficient at producing light, much energy is still being saved. What special equipment is used for dimming fluorescent lamps? The use of special dimming ballasts, which replace the standard ballast and must be compatible with the dimming control device. Authorlkillebr ID100617 Card SetCh. 10 & 11 Descriptionlighting Updated2011-09-11T22:58:39Z Show Answers