them when an electric current passes between two electrodes called cathodes in
a tube filled with low-pressure mercury vapor. It also contains inert gases
such as argon and krypton. The electric current passes through the electrodes
it excites the mercury vapor in the tube, generating radiant energy, primarily
in the ultraviolet (UV) range. The tube consists of phosphor coating on the
inside. When the UV radiated by the mercury vapor falls on the phosphor
coating, it is converted into visible light. Changing the composition of the
phosphor powder inside fluorescent tubes changes the spectrum of light
produced. Mercury is present in the lamp in both the phosphor powder and in the vapor. Whereas in incandescent lights, a filament is heated in a vacuum until it glows and gives off light and heat. During this process an enormous amount of
energy is wasted as heat.
CFLs have two main components: a
gas-filled tube and magnetic or electronic ballast. Electronic ballasts contain
a small circuit board with rectifiers, a filter capacitor and usually two
switching transistors connected as a high-frequency resonant series DC to AC
inverter. The resulting high frequency, around 40 kHz or higher, is applied to
the lamp tube. Standard CFLs do not respond well in dimming applications and
special lamps are required for dimming service.
CFLs are available in various
shapes. The standard shapes of CFL tube are single-turn double helix,
double-turn, triple-turn, quad-turn, circular, and butterfly.
consumes one third of energy than standard incandescent bulbs to produce same
amount of light.
can last about 6 times longer.
produce 70 percent less heat than standard incandescent bulbs.
cancer risk, due to leaking UV radiation.
all fluorescent lamps, CFLs contain mercury, which complicates their disposal
and if the bulbs are broken indoors, does present a health risk, especially to