The carbon button lamp is a single-electrode

Electrode

An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit...

 incandescent lamp invented by Nikola Tesla

Nikola Tesla

Nikola Tesla was a Serbian-American inventor, mechanical engineer, and electrical engineer...

 as one of a few improved lighting sources with regards to Thomas Edison's Incandescent light bulb. A carbon

Carbon

Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

 button

Button

In modern clothing and fashion design, a button is a small fastener, most commonly made of plastic, but also frequently of seashell, which secures two pieces of fabric together. In archaeology, a button can be a significant artifact. In the applied arts and in craft, a button can be an example of...

 lamp contains a small carbon sphere positioned in the center of an evacuated glass bulb. This type of lamp must be driven by high-frequency alternating current

Alternating current

In alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....

, and depends on an electric arc

Electric arc

An electric arc is an electrical breakdown of a gas which produces an ongoing plasma discharge, resulting from a current flowing through normally nonconductive media such as air. A synonym is arc discharge. An arc discharge is characterized by a lower voltage than a glow discharge, and relies on...

 or perhaps a vacuum arc

Vacuum arc

A vacuum arc can arise when the surfaces of metal electrodes in contact with a good vacuum begin to emit electrons either through heating or via an electric field that is sufficient to cause field electron emission...

 to produce high current

Electric current

Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...

 around the carbon electrode. The carbon electrode is then heated to incandescence by collisions by ions which constitute the electric current. Tesla found that these lamps could be used as powerful sources of ionizing radiation

Ionizing radiation

Ionizing radiation is radiation composed of particles that individually have sufficient energy to remove an electron from an atom or molecule. This ionization produces free radicals, which are atoms or molecules containing unpaired electrons...

.

On February, 1892, Tesla gave a lecture to the Institution of Electrical Engineers, in which he describes the carbon button lamp in detail. He also describes several variants of the lamp, one of which uses a ruby

Ruby

A ruby is a pink to blood-red colored gemstone, a variety of the mineral corundum . The red color is caused mainly by the presence of the element chromium. Its name comes from ruber, Latin for red. Other varieties of gem-quality corundum are called sapphires...

 drop in place of the carbon button. Some enthusiasts have argued that this is an early ruby laser

Ruby laser

A ruby laser is a solid-state laser that uses a synthetic ruby crystal as its gain medium. The first working laser was a ruby laser made by Theodore H. "Ted" Maiman at Hughes Research Laboratories on May 16, 1960....

.

External links

• Experiments with Alternate Currents of High Potential and High Frequency Tesla's lecture to the Institute of Electrical Engineers.