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The Light Bulb/Filament
In this
project, I will test different filaments for the incandescent light bulb. Each
filament will have a different glowing time. I will
create a vacuum to
drain the
oxygen inside the bulb so that the filament could glow longer
without oxygen. The importance of this topic to society is that in
this
project is that a may be able to
find a more convenient filament
for the incandescent light bulb. I am currently researching what to do on the
topic. I am looking
for some background knowledge
of the
experiment. The topic of finding another practical filament is important.
The filament is the
independent variable in this project. Different filaments will have different
glowing times. Modern filaments in light bulbs are usually made of metal. The
metal is usually tungsten. Tungsten is a metal with the highest melting point of
all metals. Before tungsten was carbonized bamboo, which lasted about 1200
hours. Platinum metal strips are good solutions but the high cost of it makes it
impractical for commercial use. In the early 1900’s, tungsten was also
expensive, but in 1910, William Coolidge invented a cheap method of making
tungsten. For a 120 volt 60 watt bulb the filament is usually 2 meters long. The
filament is very thin and is folded many times to make the short wire you see
inside the bulb. In light bulbs, an electrical current is passed through the
filament making it glow. But 95 percent of the power comes out as heat. Only
five percent comes out as visible light. The oxygen inside the bulb has to be
vacuumed out, or the filament will burn out fairly quickly. A filament is used
to convert electricity into light and heat. Tungsten is an element on the
periodical table of elements. It is a hard gray transition metal. Tungsten has
been proven better than carbonized bamboo. Some filaments will blacken the
bulb.
The amount of time a
bulb glows depends on the type of filament, making it the dependent variable.
The earliest were metal filaments, which burned but were not practical. Later,
platinum filaments were proven to be a good conductor but the high cost of the
metal made it impractical for commercial usage. Thomas Edison, the inventor of
which the light bulb is attributed to, tested filaments using carbonized bamboo.
Carbonized bamboo was the most practical filament at the time, which could glow
for six months. Tungsten has replaced bamboo. Most light bulbs today use
tungsten as their filament. The life of a modern light bulb varies within its
wattage. Some very low wattage light bulbs have been burning continuously for
over a hundred years. However most light bulbs burn for a typical 1000
hours.
The type of filament is very important as to how long a light bulb burns. The earliest filaments, using platinum strips burned out in just a few seconds. Later designs burned for a few minutes. But this was still not enough. Then, carbon filaments were used. The carbon makes the filament glow longer. At last, Thomas Edison made the carbonized bamboo filament. It burned for over 1200 hours. But there was filament that was not used. It was tungsten. Tungsten was tested before, but it was too expensive for commercial usage. Then one scientist made a method of making tungsten metal cheaply. This made tungsten replace bamboo in the light bulb even to today.
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