A spark gap consists of an arrangement of two conducting electrodes separated by a gap usually filled with a gas such as air. In Science and engineering, a conductor is a material which contains movable Electric charges. An electrode is an Electrical conductor used to make contact with a nonmetallic part of a circuit (e This page is about the physical properties of gas as a state of matter Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five When a suitable voltage is supplied, a spark forms, ionizing the gas and drastically reducing its electrical resistance. Electrical tension (or voltage after its SI unit, the Volt) is the difference of electrical potential between two points of an electrical An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge Electrical resistance is a ratio of the degree to which an object opposes an Electric current through it measured in Ohms Its reciprocal quantity is An electric current then flows until the path of ionized gas is broken or the current reduces below a minimum value called the 'holding current'. The holding current in a Silicon controlled rectifier (SCR is the minimum current which must pass through the device in order for it to remain in the 'ON' state This usually happens when the voltage drops, but in some cases occurs when the heated gas rises, stretching out and then breaking the filament of ionized gas. Electrical tension (or voltage after its SI unit, the Volt) is the difference of electrical potential between two points of an electrical Usually the action of ionizing the gas is violent and disruptive, often leading to sound (ranging from a snap for a spark plug to thunder for a lightning discharge), light and heat. Sound' is Vibration transmitted through a Solid, Liquid, or Gas; particularly sound means those vibrations composed of Frequencies A spark plug (also very rarely nowadays in British English: a sparking plug) is an electrical device that fits into the Cylinder Thunder is the sound made by Lightning. Depending on the nature of the lightning and distance of the listener it can range from a sharp Lightning is an atmospheric discharge of Electricity, which typically occurs during Thunderstorms and sometimes during volcanic eruptions or Light, or visible light, is Electromagnetic radiation of a Wavelength that is visible to the Human eye (about 400–700 In Physics, heat, symbolized by Q, is Energy transferred from one body or system to another due to a difference in Temperature

Contents 1 Spark visibility 2 Applications 2.1 Ignition devices 2.2 Radio transmitters 2.3 Spark gaps as protective devices 2.4 Power-switching devices 2.5 Visual entertainment 3 See also 4 External links 5 References

Spark visibility

The emitted light does not come from the electron current, but the material medium fluorescing in response to collisions from the electrons exciting its electron orbitals to high, excited states and dropping them repeatedly. Fluorescence is a Luminescence that is mostly found as an The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J An atomic orbital is a Mathematical function that describes the wave-like behavior of an electron in an atom It is possible for a spark to form in a vacuum. This vacuum means "absence of matter" or "an empty area or space" for the cleaning appliance see Vacuum cleaner. Without intervening matter capable of electromagnetic transitions, the spark will be invisible (see vacuum arc). Electromagnetism is the Physics of the Electromagnetic field: a field which exerts a Force on particles that possess the property of A vacuum arc can arise when the surfaces of Metal Electrodes in contact with a good Vacuum begin to emit Electrons either through heating (

Applications

Spark gaps are essential to the functioning of a number of electronic devices.

Ignition devices

A spark plug uses a spark gap to initiate combustion. Combustion or burning is a complex sequence of Exothermic chemical reactions between a Fuel and an Oxidant accompanied by the production of The heat of the ionization trail ignites a fuel-air mixture inside an internal combustion engine, or a burner in a furnace, oven, or stove. The internal combustion engine is an engine in which the Combustion of Fuel and an Oxidizer (typically air occurs in a confined space called a

Radio transmitters

A spark radiates energy throughout the electromagnetic spectrum. The electromagnetic (EM spectrum is the range of all possible Electromagnetic radiation frequencies Nowadays, this is usually regarded as radio frequency interference and is suppressed, but in the early days of radio communications, this was the means by which radio signals were transmitted, in the spark-gap transmitter. A spark-gap transmitter is a device for generating Radio frequency electromagnetic waves. Many radio spark gaps include cooling devices such as the rotary gap and heat sinks, since the spark gap becomes quite hot under continuous use at high power. A spark-gap transmitter is a device for generating Radio frequency electromagnetic waves. A heat sink (or heatsink) is an environment or object that absorbs and dissipates heat from another object using Thermal contact (either direct or radiant

Spark gaps as protective devices

Spark gaps are frequently used to prevent voltage surges from damaging equipment. In electrical engineering spikes are fast short duration electrical transients in voltage ( voltage spikes) current ( current spike) or transferred energy Spark gaps are used in high-voltage switches, for example, in power plants and electrical substations. A switch is a mechanical device used to connect and disconnect an electric Circuit at will A power station (also referred to as generating station, power plant or powerhouse) is an industrial facility for the generation of An electrical substation is a subsidiary station of an Electricity generation, transmission and distribution system where Voltage Such switches are constructed with a large, remote-operated switching blade with a hinge as one contact and two leaf springs holding the other end as second contact. Originally called laminated or carriage spring, a leaf spring is a simple form of spring, commonly used for the suspension in If the blade is opened, a spark may keep the connection between blade and spring conducting. (The spark ionizes the air, which becomes conductive, allowing an arc to form, which sustains ionization and hence conduction. ) Here, a Jacob's ladder (see below) on top of the switch will pull the arc apart and so extinguish it. You might also find small Jacob's ladders mounted on top of ceramic insulators of high-voltage pylons. If a spark should ever manage to jump over the insulator and give rise to an arc, it will be extinguished.

Smaller spark gaps are often used to protect sensitive electrical or electronic equipment from high voltage surges. When the Voltage in a circuit or part of it is raised above its upper design limit this is known as overvoltage. In sophisticated versions of these devices (called gas tube arresters), a small spark gap breaks down during an abnormal voltage surge, safely shunting the surge to ground and thereby protecting the equipment. These devices are commonly used for telephone lines as they enter a building; the spark gaps help protect the building and internal telephone circuits from the effects of lightning strikes. Basic principle A traditional landline telephone system also known as "plain old telephone service" (POTS, commonly handles both signaling and audio information Lightning is an atmospheric discharge of Electricity, which typically occurs during Thunderstorms and sometimes during volcanic eruptions or Less sophisticated (and much less expensive) spark gaps are made using modified ceramic capacitors; in these devices, the spark gap is simply an air gap sawn between the two lead wires that connect the capacitor to the circuit. The word ceramic is derived from the Greek word κεραμικός ( keramikos) A capacitor is a passive electrical component that can store Energy in the Electric field between a pair of conductors A saw is a Tool that uses a hard blade or wire with an abrasive edge to cut through softer materials A voltage surge causes a spark which jumps from lead wire to lead wire across the gap left by the sawing process. These low-cost devices are often used to prevent damaging arcs between the elements of the electron gun(s) within a cathode ray tube (CRT). The cathode ray tube (CRT is a Vacuum tube containing an Electron gun (a source of electrons and a Fluorescent screen with internal or The cathode ray tube (CRT is a Vacuum tube containing an Electron gun (a source of electrons and a Fluorescent screen with internal or

Small spark gaps are very common in telephone switchboards, as the long phone cables are very susceptible to induced surges from lightning strikes. A switchboard (also called a manual exchange) was a device used to connect a group of Telephones manually to one another or to an outside connection within and between Lightning is an atmospheric discharge of Electricity, which typically occurs during Thunderstorms and sometimes during volcanic eruptions or Larger spark gaps are used to protect power lines. Electric power transmission, a process in the delivery of Electricity to consumers is the bulk transfer of electrical power

Transils and trisils are the solid-state alternatives to spark gaps for lower-power applications. A transient voltage suppression (TVS diode is an Electronic component used to protect sensitive Electronics from Voltage spikes induced on connected wires A Trisil is trade name for a thyristor surge protection device, an electronic component designed to protect electronic circuits against Overvoltage. Neon bulbs are also used for this purpose. A neon lamp is a Gas discharge Lamp containing primarily Neon gas at low Pressure.

Power-switching devices

Special purpose, high-energy triggerable spark gaps are also used to rapidly switch high voltages and very high currents for certain pulsed power applications, such as pulsed lasers, railguns, fusion and ultrastrong pulsed magnetic field research, and in the triggering of nuclear bombs. A laser is a device that emits Light ( Electromagnetic radiation) through a process called Stimulated emission. A railgun is a purely electrical Gun that accelerates a conductive projectile along a pair of metal rails using the same principles as the Homopolar motor. The Z machine is the largest X-ray generator in the world and is designed to test materials in conditions of extreme temperature and pressure In Physics, a magnetic field is a Vector field that permeates space and which can exert a magnetic force on moving Electric charges The exploding-bridgewire detonator ( EBW, also known as exploding wire detonator) was invented by Luis Alvarez and Lawrence Johnson for the These often have higher power capabilities than any thyristor, thyratron, krytron, or sprytron. The thyristor is a solid-state Semiconductor device with four layers of alternating N and P-type material A thyratron is a type of Gas filled tube used as a high Energy electrical Switch and controlled Rectifier. The Krytron is a cold-cathode Gas filled tube intended for use as a very high-speed switch and was one of the earliest developments of the EG&G Corporation. The Krytron is a cold-cathode Gas filled tube intended for use as a very high-speed switch and was one of the earliest developments of the EG&G Corporation. One such type of switch is known as a trigatron. A trigatron is a type of triggerable Spark gap switch designed for high current and high voltage (usually 10-100 kV and 20-100 kA though devices in the megaampere range exist

Visual entertainment

A Jacob's ladder (more formally, a high voltage traveling arc) is a device for producing a continuous train of large sparks which rise upwards. The spark gap is formed by two wires, approximately vertical but gradually diverging away from each other towards the top.

When high voltage is applied to the gap, a spark forms across the bottom of the wires where they are nearest each other, rapidly changing to an 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 Air breaks down at about 30kV/cm,^[1] depending on humidity, temperature, etc. Apart from the anode and cathode voltage drops, the arc behaves almost as a short circuit, drawing as much current as the electrical power supply can deliver, and the heavy load dramatically reduces the voltage across the gap. Short Circuit is a 1986 comedy Science fiction film starring Ally Sheedy and Steve Guttenberg and directed by Power supply is a reference to a source of Electrical power. A device or system that supplies Electrical or other types of Energy to an output load If an electric circuit has a well-defined output terminal the circuit connected to this terminal (or its Input impedance) is the load.

The heated, ionized air rises, carrying the current path with it. As the trail of ionization gets longer, it becomes more unstable, finally breaking. The voltage across the electrodes then rises and the spark re-forms at the bottom of the device.

This cycle leads to an exotic-looking display of electric white, yellow, blue or purple arcs which is often seen in movies about mad scientists. White is a Color, the perception which is evoked by Light that stimulates all three types of color sensitive Cone cells in the Human eye Yellow is the Color evoked by light that stimulates both the L and M (long and medium wavelength Cone cells of the Retina about equally Blue is a Colour, the Perception of which is evoked by Purple is a general term for the range of shades of Color occurring between Red and Blue. The device was a staple in schools and science fairs of the 1950s and 1960s, typically constructed out of a Model T spark coil, or any other source of high voltage in the 10,000 volt - 30,000 volt range, like a neon sign transformer or circuit (10-30 kV) or a television picture tube circuit (flyback transformer) (10-28 kV), and two coat hangers or rods built into a "V" shape. A science fair is generally a competition where contestants present their Science project results in the form of a report display board and models that they have created The 1950s Decade refers to the years of 1950 to 1959 inclusive The 1960s decade refers to the years from the beginning of 1960 to the end of 1969 An ignition system is a system for igniting a fuel-air mixture A Neon Sign Transformer (NST is a Transformer made for the purpose of powering a Neon sign. A flyback or line output transformer ( FBT or LOPT) is a type of Transformer used in the Power supply of a Cathode ray tube For larger ladders, microwave oven transformers connected in series or utility pole transformers (pole pigs) run in reverse (step-up) are used. The sparks can burn through thin paper and plastic and start fires; contact with the exposed high voltage can be lethal.

See also

• Arcing horns
• Corona discharge
• Electric arc
• Ignition system
• Model T Spark Coil
• List of electronics topics
• Plasma arc loudspeakers
• Radar
• Spark-gap transmitter
• Spark plug
• Tesla coil
• Vacuum arc

External links

• Videos of 230,000 volt 3-phase "Jacobs Ladder" and HUGE unintentional 500,000 volt power arc
• Do-it-yourself five foot tall Jacob's Ladder

References

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