Thomas Edison had seen great changes in the world in his lifetime, and he was responsible for many of them.
When he was born in 1847 there was no electricity in homes.
In 1878 he formed the Edison Light Company, with the financial support of some of New York’s richest businessmen, to research the electric lamp (a device that gives off light; commonly called an electric light bulb). Edison did not yet have a lamp or an electric system, and his investors became impatient waiting for his invention to be created.
Edison’s electric lamp was missing the right material for the filament.
The filament is the fine thread in a lamp that gets hot and gives off light. He needed a material that would get hot when a small amount of electricity (electric energy) moves through it.
The filament material also had to be readily available so his lamps would not be too expensive.
Edison tested the fibers from thousands of plants collected from different parts of the world. He tried other materials, and thought of using tungsten (a metal that has the highest melting point of all metals), which is used in bulbs today, but at that time he did not have the tools to made a thin thread from this metal. Edison finally burned a piece of cardboard producing a thin hair-like piece of carbon. With this as the filament the lamp burned for one hundred and seventy hours.
The emission of light due to the high temperature of an object is called incandescence. Edison’s lamp was not the first electric lamp, nor the first incandescent lamp but it was what Edison had promised–a lamp that was practical and cheap. Edison’s first commercial lamps were installed on the steamship Columbia and later in a New York City factory. With this invention the age of electricity began.
Before Edison started work on his lamp, he knew that the type of electric circuit (path of an electric current) used at that time, called a series circuit (acircuit with only one path for the electric current), was not very practical. Lamps in a series are connected one after the other so that the same electricity that flows thro
ugh the first lamp goes into the second lamp, and so on. Edison’s first great idea for electric lighting was that lamps be connected in a parallel circuit (circuit in which the electric current divides and follows two or more paths). The path of the electricity in this type of circuit allowed electricity to flow through different branches and lamps on one branch could be turned off without affecting lamps on the other branches.
For more information and investigations about Edison, see
THOMAS EDISON INDEX