A Little History
It was in 1879 that Thomas EDISON patented the first light bulb. It is a device contained in a glass envelope that gives light through electricity. It is known under the Latin name ampulla.
But contrary to popular belief, it was not Thomas Edison who invented the light bulb, but rather Joseph Swan, who discovered the classical incandescent lamp in 1878. Thomas Edison brought a work of improvement on this invention Revolutionary in 1879. Following a lawsuit, the two inventors obtained the right to make their own light bulbs. Swan then invented the bayonet pellet and Edison screwed it up.
The Incandescent Lamp, The Oldest Lamp
Unlike LED bulbs defined here, the oldest bulb is therefore the incandescent lamp. It consists of a glass bulb and a metal base. On the base, two points of electrical contacts allow the passage of the current. Inside the bulb, filled with an inert gas (argon, krypton) without oxygen, a metallic filament passes through the electric current.
The Secret Of Light
The filament is therefore heated to high temperature, which produces light. This filament is generally made of tungsten, the metal with the highest melting point (tungsten melts at 3422 ° C while iron melts at 1538 ° C).
The filament reaches a very high temperature (close to 2500 ° C.), which explains why it is burned when an illuminated bulb is touched. The temperature is such that if the bulb was made of oxygen, it would burn instantaneously. It is for this reason that inside the bulb there are either vacuum or rare gases. The heated filament emits light: this is called incandescence.
From Bamboo To Tungsten
To develop a filament capable of emitting light in the passage of electricity, Thomas Edison has searched for the ideal material in the four corners of the world. After testing 6000 plant samples and making some 1200 attempts, he finally opted for a carbonized bamboo filament. The incandescent light bulb we know today uses a tungsten filament.Tungsten bulbs appeared at the beginning of the 20th century.
The New Bulbs
The lamps have been improved over the course of research. There are now on the market new types of bulbs: halogen, fluo-compact … It is no longer a filament that heats but the gas contained inside the bulb. These new lamps save energy while increasing their lifetime and efficiency. In order to save energy, incandescent bulbs are banned in Europe since August 31, 2012.