The Incandescent Bulb

Over the next few weeks Primelite will be taking a look at the different types of light bulbs. From Incandescent to LED, lighting has changed immensely over the past 200+ years. This week we take a look at Incandescent Bulbs.

What is an Incandescent Bulb

But before we delve in incandescent’s history lets take a look at what is an incandescent bulb.

1) Outline of Glass bulb
2) Low pressure inert gas (argon, nitrogen, krypton, xenon)
3) Tungsten filament
4) Contact wire (goes out of stem)
5) Contact wire (goes into stem)
6) Support wires (one end embedded in stem; conduct no current)
7) Stem (glass mount)
8) Contact wire (goes out of stem)
9) Cap (sleeve)
10) Insulation (vitrite)
11) Electrical contact

 “The incandescent light bulb turns electricity into light by sending the electric current through a thin wire called a filament. Filament is made up mostly of tungsten, a type of metal. The resistance of the filament heats the bulb up. Eventually the filament gets so hot that it glows, producing light.”

“The filament needs to be protected from oxygen in the air, so it is inside the bulb, and the air in the bulb is either removed (a vacuum) or more often, replaced with a gas that doesn’t affect anything (inert), like neon or argon. Only about 3% of the energy that goes into an incandescent light bulb actually makes light, the rest makes heat.”*

History of the Incandescent Bulb

Most people associate the incandescent bulb and early lighting with Thomas Edison. While Edison, and his company, did contribute to the design of the light bulb he was not the inventor, nor the first to use an incandescent bulb.

In 1802 Humphry Davy, who at the time had the most powerful electrical battery, experimented by passing electrical current through a thin strip of platinum. These experiments would lead to the first incandescent bulb. While the platinum filament worked, it was expensive. Over the next 75 years there would scores of experiments, worldwide, leading to the refinement of the incandescent bulb.

In 1850 a British physicist and chemist named Joseph Swan began experimenting with different filament materials, even receiving a British patent for his invention. Swan’s own home would eventually become the first home to be lit by a lightbulb. In 1881 the Savoy Theatre in London became the first public building that was lit entirely by the electric incandescent bulb.

At about this same time Thomas Edison was conducting his own experiments. Edison and his company, United States Electric Light Company, experimented with filaments made of platimun, different metals, carbonized “cotton and linen thread”, wood splints, papers, even bamboo. Edison was eventually awarded a US patent for an electric lamp using “a carbon filament or strip coiled and connected … to plantina contact wires.”**

Thomas Edison’s bulbs would eventually triumph when he created a bulb with a pure vacuum inside. The removal of air from the bulb would allow the filament to glow for a longer period of time. Over the next 10 years there would be multiple lawsuits involving the different bulb and filament patents with a judge eventually ruling in Thomas Edison’s favor.

Continued experimentation would lead to the development of the tungsten filament. The use of the tungsten filament  and the introduction of an inert gas into the bulbs vacuum would become the final element in the maturation of the incandescent bulb. These refinements became the standard used in incandescent light bulbs and are still used today.

Consumption of incandescent light bulbs grew rapidly in the US. In 1885, an estimated 300,000 general lighting service lamps were sold, all with carbon filaments. When tungsten filaments were introduced, about 50 million lamp sockets existed in the US. In 1914, 88.5 million lamps were used, (only 15% with carbon filaments), and by 1945, annual sales of lamps were 795 million (more than 5 lamps per person per year).

Today incandescent bulbs are being phased out due to their inefficiency and are being replaced with compact fluorescent lamps (CFL) and LEDs.

Primelite looks at the light bulb:

• Incandescent bulbs
• Reflectorized
• Tungsten-halogen
• Fluorescent bulbs
• Compact Fluorescent Lamps (CFLs)
• High-Intensity Discharge (HID)
• Light Emitting Diodes (LEDs)

Sources:
Photo: Incandescent bulb – Wikipedia: Incandescent Light Bulb
Photo: Incandescent bulb cutaway – Wikipedia: Incandescent Bulb
Photo: Joseph Swan – Wikipedia: Joseph Wilson Swan
Photo: Thomas Edison – Wikipedia: Thomas Edison

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* Wikipedia : Light Bulb
** Wikipedia: Incandescent Light Bulb