come in various shapes, sizes, wattages, and types. The most common bulb
in use today is the incandescent type. People use incandescent light bulbs
to light their homes, offices, yards, and even the interior of their appliances.
first development in electric lighting was the arc lamp, first demonstrated
in 1801 by Sir Humphry Davy, in which an electric current bridges a gap
between two carbon rods and forms a bright discharge called an arc. The
early lamps of this type had an open arc; later ones, enclosed in glass,
were more practicable.
| The American
electrician Moses G. Farmer developed the incandescent electric lamp, in
which an electric current passing through a resistance filament enclosed
in a vacuum tube heats the filament until it glows, in 1858-59; his version
was not practical. Sir Joseph Swan in England and Thomas Edison in the United
States, working independently, developed lamps of this kind; the lamp patented
by Edison in 1879 was the first widely marketed incandescent lamp and was
the forerunner of the modern lamp that utilizes a filament of drawn tungsten
sealed airtight in a glass envelope. The American chemist Irving Langmuir
invented a gas-filled incandescent lamp in 1913.
Electric incandescent lamp based on a glowing metallic filament
enclosed within a glass shell of a semi-vacuum that contains an
inert gas such as nitrogen.
Incandescent lights produce light by heating a suitable material
to a high temperature. When any solid or gas is heated, commonly
by combustion or resistance to an electric current. Common light
bulbs use a tungsten-carbon filament because of its strength and
high melt-point of 3,400º.
The bulb requires an airtight seal to contain the gas. An optimum
amount of vacuum is necessary to produce the desired amount of
A base metallic base holds the glass bulb and tungsten filament.
A socket holds the base to make the electrical connection required
to produce the light.
| Light bulbs
are everywhere in our everyday life. They are simple and elegant, and we
consider them necessary for modern existence. Light bulbs perform both utilitarian
and decorative functions, but by and large, we tend to spend little time
thinking about them.
| The common
incandescent light bulb was revolutionary a little over a century ago, but
today they are one of the humble features of modern life we couldn't live