Electric discharge describes any flow of electric charge through a gas, liquid or solid. Electric discharges include:

• Electric glow discharge
  Electric glow discharge
  An electric glow discharge is a plasma formed by the passage of current at 100 V to several kV through a gas, often argon or another noble gas. It is found in products such as neon lamps and plasma-screen televisions, and is used in plasma physics and analytical chemistry.-Basic operating...
  
  
• 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...
  
  
• Electrostatic discharge
  Electrostatic discharge
  Electrostatic discharge is a serious issue in solid state electronics, such as integrated circuits. Integrated circuits are made from semiconductor materials such as silicon and insulating materials such as silicon dioxide...
  
  
• Electric discharge in gases
  Electric discharge in gases
  Electric discharge in gases occurs when electric current flows through a gaseous medium. Depending on several factors, the discharge may radiate visible light.-Discharge types:...
  
  
• Leader (spark)
  Leader (spark)
  A leader is a hot, highly conductive channel of plasma that plays a critical part during dielectric breakdown within in a long electric spark.-Mechanism:...
  
  
• Partial discharge
  Partial discharge
  In electrical engineering, partial discharge is a localised dielectric breakdown of a small portion of a solid or fluid electrical insulation system under high voltage stress, which does not bridge the space between two conductors...
  
  
• Corona discharge
  Corona discharge
  In electricity, a corona discharge is an electrical discharge brought on by the ionization of a fluid surrounding a conductor that is electrically energized...
  
  
• 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...
  
  
• Townsend discharge
  Townsend discharge
  The Townsend discharge is a gas ionization process where an initially very small amount of free electrons, accelerated by a sufficiently strong electric field, give rise to electrical conduction through a gas by avalanche multiplication: when the number of free charges drops or the electric field...
  
  
• Dielectric barrier discharge
  Dielectric barrier discharge
  Dielectric-barrier discharge is the electrical discharge between two electrodes separated by an insulating dielectric barrier. Originally called silent discharge and also known as ozone production discharge or partial discharge, it was first reported by Ernst Werner von Siemens in 1857.- Process...
  
  
• Brush discharge
  Brush discharge
  A brush discharge is a type of corona discharge that takes place between two electrodes embedded in a nonconducting medium and is characterized by nonsparking, faintly luciferous furcations composed of ionized particles....
  
  

Applications

The properties and effects of electric discharges are useful over a wide range of magnitudes. Tiny pulses of current are used to detect 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...

 in a Geiger–Müller tube

Geiger–Müller tube

A Geiger–Müller tube is the sensing element of a Geiger counter instrument that can detect a single particle of ionizing radiation, and typically produce an audible click for each. It was named for Hans Geiger who invented the device in 1908, and Walther Müller who collaborated with Geiger in...

. A low steady current can be used to ilustrate the spectrum of gases in a Gas-filled tube

Gas-filled tube

A gas-filled tube, also known as a discharge tube, is an arrangement of electrodes in a gas within an insulating, temperature-resistant envelope. Although the envelope is typically glass, power tubes often use ceramics, and military tubes often use glass-lined metal...

. A neon lamp

Neon lamp

A neon lamp is a miniature gas discharge lamp that typically contains neon gas at a low pressure in a glass capsule. Only a thin region adjacent to the electrodes glows in these lamps, which distinguishes them from the much longer and brighter neon tubes used for signage...

 is an example of a gas-discharge lamp

Gas-discharge lamp

Gas-discharge lamps are a family of artificial light sources that generate light by sending an electrical discharge through an ionized gas, i.e. a plasma. The character of the gas discharge critically depends on the frequency or modulation of the current: see the entry on a frequency classification...

, useful both for illumination and as a voltage regulator

Voltage regulator

A voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level. A voltage regulator may be a simple "feed-forward" design or may include negative feedback control loops. It may use an electromechanical mechanism, or electronic components...

. A flashtube

Flashtube

A flashtube, also called a flashlamp, is an electric arc lamp designed to produce extremely intense, incoherent, full-spectrum white light for very short durations. Flashtubes are made of a length of glass tubing with electrodes at either end and are filled with a gas that, when triggered, ionizes...

 generates a short pulse of intense light useful for photography

Photography

Photography is the art, science and practice of creating durable images by recording light or other electromagnetic radiation, either electronically by means of an image sensor or chemically by means of a light-sensitive material such as photographic film...

 by sending a heavy current through a gas arc discharge. Corona discharge

Corona discharge

In electricity, a corona discharge is an electrical discharge brought on by the ionization of a fluid surrounding a conductor that is electrically energized...

s are used in photocopier

Photocopier

A photocopier is a machine that makes paper copies of documents and other visual images quickly and cheaply. Most current photocopiers use a technology called xerography, a dry process using heat...

s.

Electric discharges can convey substantial energy to the electrodes at the ends of the discharge. A spark gap

Spark gap

A spark gap consists of an arrangement of two conducting electrodes separated by a gap usually filled with a gas such as air, designed to allow an electric spark to pass between the conductors. When the voltage difference between the conductors exceeds the gap's breakdown voltage, a spark forms,...

 is used in internal combustion engines to ignite the fuel/air mixture on every power stroke. Spark gaps are also used to switch heavy currents in a Marx generator

Marx generator

A Marx generator is an electrical circuit first described by Erwin Otto Marx in 1924. Its purpose is to generate a high-voltage pulse. Marx generators are often used to simulate the effects of lightning on power line gear and aviation equipment....

 and to protect electrical appratus.In electric discharge machining, multiple tiny electric arcs are used to erode a conductive workpiece to a finished shape. Arc welding

Arc welding

Arc welding is a type of welding that uses a welding power supply to create an electric arc between an electrode and the base material to melt the metals at the welding point. They can use either direct or alternating current, and consumable or non-consumable electrodes...

 is used to assemble heavy steel structures, where the base metal is heated to melting by the heat of the arc. An electric arc furnace

Electric arc furnace

An electric arc furnace is a furnace that heats charged material by means of an electric arc.Arc furnaces range in size from small units of approximately one ton capacity up to about 400 ton units used for secondary steelmaking...

 sustains arc currents of tens of thousands of amperes and is used for steelmaking and production of alloys and other products.

See also

• Electrical breakdown
  Electrical breakdown
  The term electrical breakdown or electric breakdown has several similar but distinctly different meanings. For example, the term can apply to the failure of an electric circuit....
  
  
• E/N ratio
• Lichtenberg figure
  Lichtenberg figure
  Lichtenberg figures are branching electric discharges that sometimes appear on the surface or the interior of insulating materials. They are named after the German physicist Georg Christoph Lichtenberg, who originally discovered and studied them...
  
  
• Space charge
  Space charge
  Space charge is a concept in which excess electric charge is treated as a continuum of charge distributed over a region of space rather than distinct point-like charges...
  
  
• Debye sheath
  Debye sheath
  The Debye sheath is a layer in a plasma which has a greater density of positive ions, and hence an overall excess positive charge, that balances an opposite negative charge on the surface of a material with which it is in contact...