the science that measures light. Light is really visible energy.
Light emitted in a specific direction by a source (luminance intensity) measured in candelas (cd)
light emitted in all directions by a source (luminous flux) measured in lumens
density of light at any given point on a surface. Measured in footcandles. (fc)
accepted term for light that is reflected from a surfac in a given direction
total quantity of light emitted, reflected, or transmitted in all directions from a surface. measured in lumens per square foot (lm/ft2)
flow of electricity
potential of flow 120/240 volt
rate of flow, volt per second
path that current flows
material that allows flow
rate of change.
Volts x amp = watts
amount of electrical power consumed over a period of time
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 voltage
2) 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.