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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. When a suitable voltage Voltage

Voltage is the difference of electrical potential [i] between two points of an electrical network [i] ... 

 is supplied, a spark Spark

The word spark has several meanings: ... 

 forms, ionizing the gas and drastically reducing its electrical resistance Electrical resistance

Electrical resistance is a measure of the degree to which an object opposes the passage of an electric current [i] ... 

. 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'. This usually happens when the voltage Voltage

Voltage is the difference of electrical potential [i] between two points of an electrical network [i] ... 

 drops, but in some cases occurs when the heated gas rises, stretching out and then breaking the filament of ionized gas.

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A spark gap consists of an arrangement of two conducting electrodes separated by a gap usually filled with a gas such as air. When a suitable voltage Voltage

Voltage is the difference of electrical potential [i] between two points of an electrical network [i] ... 

 is supplied, a spark Spark

The word spark has several meanings:
... 

 forms, ionizing the gas and drastically reducing its electrical resistance Electrical resistance

Electrical resistance is a measure of the degree to which an object opposes the passage of an electric current [i]... 

. 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'. This usually happens when the voltage Voltage

Voltage is the difference of electrical potential [i] between two points of an electrical network [i] ... 

 drops, but in some cases occurs when the heated gas rises, stretching out and then breaking the filament of ionized gas. Usually the action of ionizing the gas is violent and disruptive, often leading to sound Sound

Sound is a disturbance of mechanical energy [i] that propagates through matter [i] as a wave [i]. ... 

 , light Light

Light is electromagnetic radiation [i] with a wavelength [i] that is visible to the eye [i] or, in a technical [i] ... 

 and heat Heat

In physics [i], heat, symbolized by Q, is defined as energy in transit. ... 

.

Spark visibility


The emitted light does not come from the electron current, but the material medium fluorescing Fluorescence

Fluorescence is a luminescence [i] that is mostly found as an optical phenomenon [i] in cold bodies, in ... 

 in response to collisions from the electrons exciting its electron Electron

The electron is a fundamental [i] subatomic particle [i] that carries an electric charge [i]... 

 orbital Atomic orbital

In chemistry [i], an atomic orbital is the region in which an electron [i] may be found around a single ... 

s to high, excited states and dropping them repeatedly. It is possible for a spark to form in a vacuum Vacuum

A vacuum is a volume [i] of space [i] that is substansively empty of matter [i], so that gaseous pressur ... 

 and many comprise the solar wind Solar wind

[i]s, [[carrot]... 

. Without intervening matter capable of electromagnetic transitions, the spark will be invisible Invisibility

Invisibility is the state of an object which cannot be seen [i].... 

 .

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. The heat of the ionization trail ignites a fuel-air mixture inside an internal combustion engine Internal combustion engine

The internal combustion engine is a heat engine [i] in which the burning of a fuel [i] occurs ... 

, or a burner in a furnace, oven, or stove.

Radio transmitters

A spark radiates energy throughout the electromagnetic spectrum Electromagnetic spectrum

The electromagnetic spectrum is the range of all possible electromagnetic radiation [i]. ... 

. 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 Spark-gap transmitter

The Spark-gap transmitter is a device for generating radio frequency [i] electromagnetic waves [i] ... 

. Many radio spark gaps include machined fins for cooling as the spark gap becomes quite hot with continued use.

Spark gaps as protective devices


Spark gaps are frequently used to prevent voltage surges from damaging equipment.Spark gaps are used in high-voltage switch Switch

A switch is a device for changing the course [i] of a circuit [i]. ... 

es, for example, in power plant Power station

A power station or power plant is a facility for the generation [i] of electric power [i] ... 

s and electrical substation Electrical substation

A substation is a subsidiary station of an electricity [i] generation [i], transmission [i] ... 

s. Such switches are constructed with a large, remote-operated switching blade with a hinge as one contact and two leaf spring Leaf spring

A leaf spring is a simple form of spring [i], commonly used for the suspension [i] in ... 

s holding the other end as second contact. If the blade is opened, a spark may keep the connection between blade and spring conducting. Here, a Jacob's ladder 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. In sophisticated versions of these devices , 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 Telephone

The telephone or phone is a telecommunication [i]s device which is used to transmit [i] ... 

 lines as they enter a building; the spark gaps help protect the building and internal telephone circuits from the effects of lightning Lightning

Lightning is a powerful natural electrostatic discharge [i] produced during a thunderstorm [i]. ... 

 strikes. Less sophisticated spark gaps are made using modified ceramic Ceramic

The word ceramic is derived from the Greek [i] word ?e?a???? . ... 

 capacitor Capacitor

A capacitor is an electric [i]al device that can store energy [i] in the electric field [i] between a pair of ... 

s; in these devices, the spark gap is simply an air gap sawn Saw

A saw is a tool [i] for cutting wood [i] or other material, consisting of a serrated blade [i] and worke ... 

 between the two lead wires that connect the capacitor to the circuit. 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 within a cathode ray tube Cathode ray tube

The cathode ray tube or CRT, invented by German [i] physicist [i] Karl Ferdinand Braun [i] ... 

 .

Small spark gaps are very common in telephone switchboard Telephone switchboard

A switchboard is a device used to manually connect a group of telephone [i]s from one to another or to ... 

s, as the long phone cables are very susceptible to induced surges from lightning Lightning

Lightning is a powerful natural electrostatic discharge [i] produced during a thunderstorm [i]. ... 

 strikes. Larger spark gaps are used to protect power lines.

Transils and trisils are the solid-state alternatives to spark gaps for lower-power applications. Neon bulb Neon lamp

A neon lamp is a gas discharge [i] lamp [i] containing primarily neon [i] gas at low pressure [i] ... 

s are also used for this purpose.

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 laser Laser

A laser is an optical source that emits photons [i] in a coherent [i] beam. ... 

s, railgun Railgun

A railgun is a form of gun [i] that converts electrical energy [i]—rather than the more convention ... 

s, fusion Z machine

The Z machine is the largest X-ray [i] generator in the world and is designed to test materials in condi ... 

 and ultrastrong pulsed magnetic field Magnetic field

In physics [i], a magnetic field is that part of the electromagnetic field [i] that exists when there is ... 

 research. These often have higher power capabilities than any thyristor Thyristor

The thyristor is a solid-state semiconductor device [i] with four layers of alternating N [i] ... 

, thyratron Thyratron

A thyratron is a type of gas filled tube [i] used as a high energy [i] electrical switch [i]. ... 

, krytron Krytron

The Krytron is a cold-cathode gas filled tube [i] intended for use as a very high-speed switch and was o ... 

, or sprytron Krytron

The Krytron is a cold-cathode gas filled tube [i] intended for use as a very high-speed switch and was o ... 

. One such type of switch is known as a trigatron Trigatron

A trigatron is a type of triggerable spark gap [i] switch designed for high current and high voltage,. ... 

.

Visual entertainment

A Jacob's ladder 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 Electric arc

An electric arc is an electrical breakdown [i] of a gas which produces an ongoing plasma [i] discharge [i] ... 

. Air breaks down at about 24kV/in, depending on humidity, temperature, etc. Apart from the anode and cathode voltage drops, the arc behaves almost as a short circuit Short circuit

A short circuit is an accidental low-resistance [i] connection between two nodes o... 

, drawing as much current as the electrical power supply Power supply

A power supply is a device or system that supplies electrical [i] or other types of energy [i] to an out ... 

 can deliver, and the heavy load External electric load

If an electric circuit [i] has a well-defined output terminal, the circuit connected to thi ... 

 dramatically reduces the voltage across the gap.

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 White

White is a color [i] that has high brightness but zero hue [i]. ... 

, yellow Yellow

Yellow is any color [i] of light that stimulates both the red [i] and green [i] cone cells [i] of the retina [i] ... 

,blue Blue

Blue is any of a number of similar color [i]s. ... 

 or purple arcs which is often seen in movies about mad scientist Mad scientist

A mad scientist is a stock character [i] of popular fiction [i], either villain [i]ous or ... 

s. The device was a staple in schools and science fairs of the 1950s 1950s

The 1950s was the decade spanning the years 1950 to 1959.... 

 and 1960s 1960s

The 1960s decade [i] refers to the years from 1960 [i] to 1969 [i], inclusive. ... 

, typically constructed out of a Model T spark coil Ignition system

The ignition system of an internal-combustion engine [i] is an important part of the overall engine syst ... 

, or any other source of high voltage in the 10,000 volt - 30,000 volt range, like a neon sign transformer Neon Sign Transformer

Neon Sign Transformers are iron-cored line powered high voltage transformers produced mainly for the purpose o... 

 or circuit or a television picture tube circuit , and two coat hangers or rods built into a "V" shape.
The sparks can burn through thin paper and plastic and start fires; contact with the exposed high voltage can be lethal.

Spark gaps in nature

Lightning Lightning

Lightning is a powerful natural electrostatic discharge [i] produced during a thunderstorm [i]. ... 

 is a large spark leaping between a cloud Cloud

A cloud is a visible mass of condensed droplets [i] or frozen crystal [i]s suspended in the atmosphere [i] ... 

 and the earth Earth

Earth is the third planet [i] in the solar system [i] in terms of distance from the Sun [i], and the fi ... 

 or between clouds.

See also

  • Arcing horns
  • Corona discharge
  • Electric arc Electric arc

    An electric arc is an electrical breakdown [i] of a gas which produces an ongoing plasma [i] discharge [i] ... 

  • Ignition system Ignition system

    The ignition system of an internal-combustion engine [i] is an important part of the overall engine syst ... 

  • Model T Spark Coil Ignition system

    The ignition system of an internal-combustion engine [i] is an important part of the overall engine syst ... 

  • List of electronics topics
  • Plasma arc loudspeakers
  • Radar Radar

    RADAR is a system that uses radio [i] waves to detect, determine the direction and distance and/or speed ... 

  • Spark-gap transmitter Spark-gap transmitter

    The Spark-gap transmitter is a device for generating radio frequency [i] electromagnetic waves [i] ... 

  • Spark plug Spark plug

    A spark plug is an electrical device that fits into the cylinder head [i] of some internal combustion engine [i] ... 

  • Tesla coil Tesla coil

    A Tesla coil is a category of disruptive discharge [i] transformer [i] coils, named after their inventor ... 

  • Vacuum arc

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