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Este artículo trata sobre chispas eléctricas. Para otros tipos de chispas, consulte Spark .
Una chispa en una bujía
El rayo es un ejemplo natural de chispa eléctrica.

Una chispa eléctrica es una descarga eléctrica abrupta que ocurre cuando un campo eléctrico suficientemente alto crea un canal ionizado y eléctricamente conductor a través de un medio normalmente aislante, a menudo aire u otros gases o mezclas de gases. Michael Faraday describió este fenómeno como "el hermoso destello de luz que acompaña a la descarga de electricidad común". [1]

La rápida transición de un estado no conductor a uno conductor produce una breve emisión de luz y un crujido agudo o un chasquido. Se crea una chispa cuando el campo eléctrico aplicado excede la fuerza de ruptura dieléctrica del medio intermedio. Para el aire, la resistencia a la ruptura es de aproximadamente 30 kV / cm al nivel del mar. [2] Experimentalmente, esta cifra tiende a diferir dependiendo de la humedad, la presión atmosférica, la forma de los electrodos (aguja y plano de tierra, hemisférico, etc.) y el espaciado correspondiente entre ellos e incluso el tipo de forma de onda, ya sea sinusoidal o coseno-rectangular. . En las etapas iniciales, los electrones libres en el espacio (de los rayos cósmicos o la radiación de fondo) son acelerados por el campo eléctrico. A medida que chocan con las moléculas de aire, crean iones adicionales y electrones recién liberados que también se aceleran. En algún momento, la energía térmica proporcionará una fuente de iones mucho mayor. Los electrones e iones que aumentan exponencialmente hacen que las regiones del aire en el espacio se vuelvan eléctricamente conductoras en un proceso llamado ruptura dieléctrica . Una vez que el espacio se rompe, el flujo de corriente está limitado por la carga disponible (para una descarga electrostática ) o por la impedancia de la fuente de alimentación externa.. Si la fuente de alimentación continúa suministrando corriente, la chispa evolucionará a una descarga continua llamada arco eléctrico . Una chispa eléctrica también puede ocurrir dentro de líquidos o sólidos aislantes, pero con mecanismos de ruptura diferentes a los de las chispas en los gases.

A veces, las chispas pueden ser peligrosas. Pueden provocar incendios y quemar la piel.

Los rayos son un ejemplo de una chispa eléctrica en la naturaleza, mientras que las chispas eléctricas, grandes o pequeñas, ocurren en o cerca de muchos objetos hechos por el hombre, tanto por diseño como a veces por accidente.

Historia [ editar ]

Benjamin Franklin dibujando una chispa eléctrica en su dedo desde una llave suspendida de una cuerda de cometa.

En 1671, Leibniz descubrió que las chispas estaban asociadas con fenómenos eléctricos. [3] En 1708, Samuel Wall realizó experimentos con ámbar frotado con una tela para producir chispas. [4] En 1752, Thomas-François Dalibard , actuando sobre un experimento propuesto por Benjamin Franklin , arregló que un dragón francés retirado llamado Coiffier en el pueblo de Marly recogiera rayos en una jarra de Leyden [5] probando así que los rayos y la electricidad eran equivalente. En el famoso experimento de la cometa de Franklin , extrajo con éxito chispas de una nube durante una tormenta.

Usos [ editar ]

Gas stove burner - the electric spark flame igniter is shown at the left.
Spark transmitter used for ship to shore communication up to 10 km (c. 1900)."

Ignition sources[edit]

Electric sparks are used in spark plugs in gasoline internal combustion engines to ignite fuel and air mixtures.[6] The electric discharge in a spark plug occurs between an insulated central electrode and a grounded terminal on the base of the plug. The voltage for the spark is provided by an ignition coil or magneto that is connected to the spark plug with an insulated wire.

Flame igniters use electric sparks to initiate combustion in some furnaces and gas stoves in place of a pilot flame.[7] 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.[8] This information is used to stop an ignition device from sparking after the flame is lit or restart the flame if it goes out.

Radio communications[edit]

A spark-gap transmitter uses an electric spark gap to generate radio frequency electromagnetic radiation that can be used as transmitters for wireless communication.[9] Spark gap transmitters were widely used in the first three decades of radio from 1887–1916. They were later supplanted by vacuum tube systems and by 1940 were no longer used for communication. The wide use of spark-gap transmitters led to the nickname "sparks" for a ship's radio officer.

Metalworking[edit]

Electric sparks are used in different kinds of metalworking. Electric discharge machining (EDM) is sometimes called spark machining and uses a spark discharge to remove material from a workpiece.[10] Electrical discharge machining is used for hard metals or those that are difficult to machine with traditional techniques.

Spark plasma sintering (SPS) is a sintering technique that uses a pulsed direct current that passes through a conductive powder in a graphite die.[11] SPS is faster than conventional hot isostatic pressing, where the heat is provided by external heating elements.

Chemical analysis[edit]

The light that is produced by electric sparks can be collected and used for a type of spectroscopy called spark emission spectroscopy.[12]

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).[13]

Electric sparks can also be used to create ions for mass spectrometry.[14]

Hazards[edit]

An electric spark produced by a stun gun. At 150,000 volts, the spark can easily jump a gap greater than an inch (2.5 cm).

Sparks can be hazardous to people, animals or even inanimate objects. Electric sparks can ignite flammable materials, liquids, gases and vapors. Even inadvertent static-discharges, or small sparks that occur when switching on lights or other circuits, can be enough to ignite flammable vapors from sources like gasoline, acetone, propane, or dust concentrations in the air, such as those found in flour mills or more generally in factories handling powders.[15][16]

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 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 who is in close enough proximity, 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, ablating 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.[17][18]

See also[edit]

  • Corona discharge
  • Electrical breakdown
  • Paschen's law
  • Static electricity

References[edit]

  1. ^ Faraday, Experimental Researches in Electricity, volume 1 paragraph 69.
  2. ^ Meek, J. (1940). "A Theory of Spark Discharge". Physical Review. 57 (8): 722–728. Bibcode:1940PhRv...57..722M. doi:10.1103/PhysRev.57.722.
  3. ^ Kryzhanovsky, L. N. (1989). "Mapping the history of electricity". Scientometrics. 17: 165–170. doi:10.1007/BF02017730.
  4. ^ Heilbron, J. L.; Heilborn, J. L. (1979). Electricity in the 17th and 18th centuries: a study of early Modern physics. Berkeley: University of California Press. ISBN 978-0-520-03478-5.
  5. ^ Michael Brian Schiffer, Draw the Lightning Down: Benjamin Franklin and Electrical Technology in the Age of Enlightenment. University of California Press, p 164
  6. ^ Day, John (1975). The Bosch book of the Motor Car, Its evolution and engineering development. St. Martin's Press. pp. 206–207. LCCN 75-39516. OCLC 2175044.
  7. ^ Bill Whitman; Bill Johnson; John Tomczyck (2004). Refrigeration and Air Conditioning Technology, 5E. Clifton Park, NY: Thomson Delmar Learning. pp. 677ff. ISBN 978-1-4018-3765-5.
  8. ^ Ed Sobey (2010). The Way Kitchens Work: The Science Behind the Microwave, Teflon Pan, Garbage Disposal, and More. Chicago, Ill: Chicago Review Press. p. 116. ISBN 978-1-56976-281-3.
  9. ^ Beauchamp, K. G. (2001). History of telegraphy. London: Institution of Electrical Engineers. ISBN 978-0-85296-792-8.
  10. ^ Jameson, Elman C. (2001). Electrical discharge machining. Dearborn, Mich: Society of Manufacturing Engineers. ISBN 978-0-87263-521-0.
  11. ^ Munir, Z. A.; Anselmi-Tamburini, U.; Ohyanagi, M. (2006). "The effect of electric field and pressure on the synthesis and consolidation of materials: A review of the spark plasma sintering method". Journal of Materials Science. 41 (3): 763. Bibcode:2006JMatS..41..763M. doi:10.1007/s10853-006-6555-2.
  12. ^ Walters, J. P. (1969). "Historical Advances in Spark Emission Spectroscopy". Applied Spectroscopy. 23 (4): 317–331. Bibcode:1969ApSpe..23..317W. doi:10.1366/000370269774380662.
  13. ^ Radziemski, Leon J.; Cremers, David A. (2006). Handbook of laser-induced breakdown spectroscopy. New York: John Wiley. ISBN 978-0-470-09299-6.
  14. ^ Dempster, A. J. (1936). "Ion Sources for Mass Spectroscopy". Review of Scientific Instruments. 7 (1): 46–49. Bibcode:1936RScI....7...46D. doi:10.1063/1.1752028.
  15. ^ An Introduction to Physical Science by James Shipman, Jerry D. Wilson, Charles A. Higgins, Omar Torres -- Cengage Learning 2016 Page 202
  16. ^ Dust explosion electrostatics hazardshttps://powderprocess.net/Safety/Electrostatics_Risks_ATEX_DSEAR.html
  17. ^ 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
  18. ^ Electrostatic Hazards by Günter Luttgens, Norman Wilson -- Reed Professional and Educational Publishing Ltd. 1997

External links[edit]

  • Szikrakisülés (1)...(4) Electric spark (1)...(4). Videos on the portal FizKapu (in Hungarian).