The carbon button lamp is a single-

electrode An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials ...

incandescent lamp invented by

Nikola Tesla Nikola Tesla ( ; ,"Tesla"
'' carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon makes ...

button 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 (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current (DC) which flows only in one direction. Alternating current is the form in which ...

, and depends on an

electric arc An electric arc, or arc discharge, is an electrical breakdown of a gas that produces a prolonged electrical discharge. The electric current, current through a normally Electrical conductance, nonconductive medium such as air produces a plasma (p ...

or perhaps a

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 (thermionic emission) or in an electric field that is sufficient to cause field electron emission. Once initia ...

to produce high current around the carbon electrode. The carbon electrode is then heated to

incandescence Incandescence is the emission of electromagnetic radiation (including visible light) from a hot body as a result of its high temperature. The term derives from the Latin verb ''incandescere,'' to glow white. A common use of incandescence is ...

by collisions by ions which constitute the electric current. Tesla found that these lamps could be used as powerful sources of ionizing radiation. In February, 1892, Tesla gave a lecture to the Institution of Electrical Engineers, in which he described the carbon button lamp in detail. He also described several variants of the lamp, one of which uses a

ruby A ruby is a pinkish red to blood-red colored gemstone, a variety of the mineral corundum (aluminium oxide). Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called sapp ...

drop in place of the carbon button.

External links

Experiments with Alternate Currents of High Potential and High Frequency
Tesla's lecture to the Institute of Electrical Engineers. Types of lamp {{tech-stub

See also

External links