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An electric spark is an abrupt electrical discharge that occurs when a sufficiently high electric field creates an Ionization, Electric current channel through a normally-insulating medium, often air or other gases or gas mixtures. Michael Faraday described this phenomenon as "the beautiful flash of light attending the discharge of common electricity".Faraday, Experimental Researches in Electricity, volume 1 paragraph 69.
The rapid transition from a non-conducting to a conductive state produces a brief emission of light and a sharp crack or snapping sound. A spark is created when the applied electric field exceeds the dielectric breakdown strength of the intervening medium. For air, the breakdown strength is about 30 kV/cm at sea level. Experimentally, this figure tends to differ depending upon humidity, atmospheric pressure, shape of electrodes (needle and ground-plane, hemispherical etc.) and the corresponding spacing between them and even the type of waveform, whether sinusoidal or cosine-rectangular.
At the beginning stages, free electrons in the gap (from or background radiation) are accelerated by the electrical field, resulting in a Townsend avalanche. As they collide with air molecules, they create additional ions and newly freed electrons which are also accelerated. At some point, thermal energy will provide a much greater source of ions. The exponentially-increasing electrons and ions rapidly cause regions of the air in the gap to become electrically conductive in a process called dielectric breakdown. Once the gap breaks down, Electric current is limited by the available charge (for an electrostatic discharge) or by the impedance of the external power supply. If the power supply continues to supply current, the spark will evolve into a continuous discharge called an electric arc. An electric spark can also occur within insulating liquids or solids, but with different breakdown mechanisms from sparks in gases.
Sometimes, sparks can be dangerous. They can cause fires and burn skin.
Lightning is an example of an electric spark in nature, while electric sparks, large or small, occur in or near many man-made objects, both by design and sometimes by accident.
Flame igniters use electric sparks to initiate combustion in some furnaces and in place of a pilot flame. (2025). 9781401837655, Thomson Delmar Learning. ISBN 9781401837655 Auto reignition is a safety feature that is used in some flame igniters that senses the electrical conductivity of the flame and uses this information to determine whether a burner flame is lit. This information is used to stop an ignition device from sparking after the flame is lit or restart the flame if it goes out.
Spark plasma sintering (SPS) is a sintering technique that uses a pulsed direct current that passes through a conductive powder in a graphite die. SPS is faster than conventional hot isostatic pressing, where the heat is provided by external .
A high energy pulsed laser can be used to produce an electric spark. Laser induced breakdown spectroscopy (LIBS) is a type of atomic emission spectroscopy that uses a high pulse energy laser to excite atoms in a sample. LIBS has also been called laser spark spectroscopy (LSS). (2025). 9780470092996, John Wiley. ISBN 9780470092996
Electric sparks can also be used to create for mass spectrometry. Spark discharge has been also applied in electrochemical sensing via the in-situ surface modification of disposable screen printed carbon electrodes (SPEs) with various metal and carbon sources.
Sparks often indicate the presence of a high voltage, or "potential field". The higher the voltage; the farther a spark can jump across a gap, and with enough energy supplied can lead to greater discharges such as a glow discharge or an arc. When a person is charged with high-voltage static-charges, or is in the presence of high-voltage electrical supplies, a spark can jump between a conductor and a person, allowing the release of much higher energies that can cause severe burns, shut down the heart and internal organs, or even develop into an arc flash.
High-voltage sparks, even those with low energy such as from a stun gun, can overload the conductive pathways of the nervous system, causing involuntary muscle-contractions, or interfere with vital nervous-system functions such as heart rhythm. When the energy is low enough most of it may be used just heating the air, so the spark never fully stabilizes into a glow or arc. However, sparks with very low energy still produce a "plasma tunnel" through the air, through which electricity can pass. This plasma is heated to temperatures often greater than the surface of the Sun, and can cause small, localized burns. Conductive liquids, gels or ointments are often used when applying electrodes to a person's body, preventing sparks from forming at the point of contact and damaging skin. Similarly, sparks can cause damage to metals and other conductors, ablation or pitting the surface; a phenomenon which is exploited in electric etching. Sparks also produce ozone which, in high enough concentrations, can cause respiratory discomfort or distress, itching, or tissue damage, and can be harmful to other materials such as certain plastics. Management of Hazardous Energy: Deactivation, De-Energization, Isolation, and Lock-out By Thomas Neil McManus -- CRC Press 2013 Page 79--80, 95--96, 231, 346, 778, 780 Electrostatic Hazards by Günter Luttgens, Norman Wilson -- Reed Professional and Educational Publishing Ltd. 1997
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