There are three different basic types of light bulbs, incandescent,
fluorescent, and high-intensity discharge. Each type works a
little differently. There are also differences withing each of these
groups. Bulbs come in different shapes, sizes, wattages and
voltages. There are also a number of different bases on these
different bulbs.
Incandescent
An incandescent light bulb is a glass bulb with a metal wire called
a filament inside a vacuum. As electricity flows through the
filament it heats up and glows, thereby producing light. Much of
the energy used to create the light is lost in heat which is why
incandescent are not the most efficient type of light.
Incandescent bulbs come in a variety of shapes and sizes. Some
common shapes are a round globe, like we use in a bathroom bar
type fixture. The standard pear shape used in common lighting
fixtures. Long tube shape for use in fish tank lights and wall
painting accent lights. Reflector bulbs are those found in recessed
lights. PAR or parabolic aluminized reflector bulbs can be used
to direct light and with a thick glass exterior, can be used
outdoors.
Halogen bulbs are a recent improvement on the incandescent
idea. The filament is encased in a small quartz envelope and
because it burns at a high temperature a chemical reaction occurs
causing the filament to last much longer than an ordinary
incandescent.
Fluorescent
Fluorescent light bulbs are comprised of a thin glass tube that is
coated on the inside with a white powder called phosphor. A
ballast produces a high current which passes through the bulb
and with the gas inside creates ultraviolet energy which hits the
phosphor and gets converted to light.
The fluorescent light has traditionally been used mostly in retail,
commercial and educational buildings. In recent years, with the
improvement in the quality of light from fluorescents and the
introduction of compact fluorescents, there has been a large
move into the residential market.
The advantages of fluorescent is they last much longer than
incandescent and are much more energy efficient.
HID
High intensity discharge lamps work in a similar way to
fluorescent light bulbs. They work by having electricity create an
arc which makes a gas inside a quartz envelope burn very hot
thereby producing light. This type of light is very efficient and is
used mostly in outdoor applications. Most street lighting you see
and stadium lighting is HID.
There are advantages and disadvantages with different types of
bulbs. Halogens, for instance, give a close to sunlight type of
light but the trade off is they burn very hot. Fluoresent lighting is
both economical to run and cool but generally don't come in a lot
of attractive fixtures.
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