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Light bulbs were one of the greatest inventions of all time. Until the light bulb and electricity were invented, people could see at night only with candles, fires, gaslights, or oil lamps. The electric light bulb provided brighter light so people were better able to read, sew, and do other things that required a lot of light.

Early Experiments

In the early 1800’s, inventors began experimenting with electric light. In 1808, Sir Humphrey Davy, an English chemist, discovered that an electrical arc passed between two poles produced light. Experimental arc lights were installed as public lighting in Paris, France in 1841. Other inventors in the United States and Europe also experimented with arc lights. Eventually, inventors lost interest in arc lights because they were too bright and burned out too quickly to be practical for everyday use.

By the mid-1800’s, inventors began experimenting with the incandescent light bulb, which passes electricity through a filament that is enclosed in a container, or bulb. A filament is a thinly spun thread, fiber, or wire. An electric current heats the filament to a minimum of 3,600 ºF, which causes it to give off both heat and light. The incandescent light bulb is the type most commonly used today in homes, for car headlights, and for flashlights. One problem inventors faced when the incandescent light bulb was being developed was finding the right material for a filament that would produce enough light and not burn out quickly. Another problem was inserting the filament in a bulb without oxygen, because oxygen would cause the filament to burn out.

The First Light Bulbs

The first incandescent light bulbs were operated with batteries and burned out quickly. In 1878, Thomas Edison began research to invent an incandescent light bulb that would operate with electricity and could be used in homes and businesses. Edison and his associates conducted over 3,000 experiments trying to find the best materials. It took months of research to find a filament material that would produce the best light. Eventually, in October 1879, Edison successfully produced a practical light bulb using a carbon filament made from burned sewing thread. Eventually, other materials, such as bamboo, were used for filaments because they increased the length of time a light bulb would burn. Edison’s first light bulb was made with a glass bulb that had no oxygen in it and burned for about 40 hours.

By l880, Edison had improved his light bulb so that it lasted for 1,500 hours. At this point, he began selling his light bulb to the public. Up until 1882, Edison only sold about 3,000 light bulbs to 203 customers of his electric company in New York. Ten years later, he had three million customers.

Although Edison is usually credited with inventing the light bulb, a British inventor named Joseph Swan obtained the first patent for in an incandescent light bulb in Britain one year before Edison obtained his patent in the United States. Swan sued Edison in court for infringement of his patent. Edison lost, and as part of the settlement, he was forced to take Swan as a partner in his British electric company named the Edison and Swan United Electric Company. Eventually, Edison bought out Swan’s share of the company.

How They Work and What They're Made Of

The filaments in light bulbs evaporate due to the high temperatures that are used. At first, incandescent light bulbs were made with a vacuum (no air) inside them. Later, it was discovered that filling the bulb with inert gases such as argon and nitrogen slows down evaporation of the filament. Inert gases are gases that do not react with other elements. Recently, the gas krypton has been used because it allows the filament to burn at higher temperatures which produces a brighter light.

Over the years, the materials used for filaments were improved to increase the life of the light bulb. It was thought that carbon would be the best material for filaments because it is the element with the highest melting point of 6,510 ºF. However, the problem with the carbon filament was that it evaporated quickly at high temperatures, which resulted in a short life for the light bulb. Lower temperatures were used to increase the life of the light bulb, but then the light was not as bright.

In the late 1800’s, two new filament materials were discovered which improved bulb brightness. In 1898, Karl Auer used osmium, which has a melting point of 4,890 ºF. In 1903, Siemens and Halske worked with tantalum, which melts at

5,425 ºF. These materials were an improvement over carbon because they could operate at higher temperatures with longer life and less evaporation. In 1910, William David Coolidge of the General Electric Company in New York invented the tungsten filament. Tungsten is the material still used in light bulbs today. The advantages of tungsten are that it has a high melting point

(6,170 ºF), a low evaporation rate, and is stronger than steel. Tungsten’s strength and flexibility make it a perfect material to form into filament coils.

The original light bulbs were made with clear glass bulbs. Some of Edison’s early light bulbs were covered with an outside frosting to reduce the glare. In 1924, an inventor named Pipkin developed a process to frost the inside of the light bulb. This process was better than outside frosting because it was more effective in reducing the glare. Most light bulbs used today are frosted, although clear bulbs are sometimes used for chandeliers and for appliance lights.

The amount of light given off by an incandescent light bulb depends on how much electricity it uses. The amount of light is described as watts of power. Light bulbs range from about 25 to 200 watts of power. Some light bulbs have more than one filament. These light bulbs can operate on different watts depending on whether the filaments are lit separately or together. For example, a light bulb could have a 50-watt and a 100-watt filament. Depending on what filaments were lit, the light bulb could produce 50, 100, or 150-watts of power, depending on how much light is needed.

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