Édouard Branly
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Édouard Eugène Désiré Branly (23 October 1844 – 24 March 1940) was a French inventor,
physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate caus ...
and
professor Professor (commonly abbreviated as Prof.) is an Academy, academic rank at university, universities and other post-secondary education and research institutions in most countries. Literally, ''professor'' derives from Latin as a "person who pr ...
at the
Institut Catholique de Paris The Institut Catholique de Paris (ICP), known in English as the Catholic University of Paris (and in Latin as ''Universitas catholica Parisiensis''), is a private university located in Paris, France. History: 1875–present The Institut Catholiq ...
. He is primarily known for his early involvement in
wireless telegraphy Wireless telegraphy or radiotelegraphy is transmission of text messages by radio waves, analogous to electrical telegraphy using cables. Before about 1910, the term ''wireless telegraphy'' was also used for other experimental technologies for ...
and his invention of the Branly
coherer The coherer was a primitive form of radio signal detector used in the first radio receivers during the wireless telegraphy era at the beginning of the 20th century. Its use in radio was based on the 1890 findings of French physicist Édouard Bran ...
around 1890.


Biography

He was born on 23 October 1844 and died on 24 March 1940. His funeral was at the
Notre Dame cathedral Notre-Dame de Paris (; meaning "Our Lady of Paris"), referred to simply as Notre-Dame, is a medieval Catholic cathedral on the Île de la Cité (an island in the Seine River), in the 4th arrondissement of Paris. The cathedral, dedicated to the ...
in Paris and was attended by the
President of France The president of France, officially the president of the French Republic (french: Président de la République française), is the executive head of state of France, and the commander-in-chief of the French Armed Forces. As the presidency i ...
,
Albert Lebrun Albert François Lebrun (; 29 August 1871 – 6 March 1950) was a French politician, President of France from 1932 to 1940. He was the last president of the Third Republic. He was a member of the centre-right Democratic Republican Alliance (AR ...
. He was interred in
Père Lachaise Cemetery Père Lachaise Cemetery (french: Cimetière du Père-Lachaise ; formerly , "East Cemetery") is the largest cemetery in Paris, France (). With more than 3.5 million visitors annually, it is the most visited necropolis in the world. Notable figures ...
in Paris.


Coherer

Temistocle Calzecchi-Onesti's experiments with tubes of metal filings, as reported in "Il Nuovo Cimento" in 1884, led to the development of the first radio wave detector, the ''coherer'', by Branly some years later. It was the first widely used
detector A sensor is a device that produces an output signal for the purpose of sensing a physical phenomenon. In the broadest definition, a sensor is a device, module, machine, or subsystem that detects events or changes in its environment and sends ...
for radio communication. This consisted of iron filings contained in an insulating tube with two electrodes that will conduct an electric current under the action of an applied electrical signal. The operation of the coherer is based upon the large
electrical contact resistance The term contact resistance refers to the contribution to the total resistance of a system which can be attributed to the contacting interfaces of electrical leads and connections as opposed to the intrinsic resistance. This effect is describe ...
offered to the passage of electric current by loose metal filings, which decreases when
direct current Direct current (DC) is one-directional flow of electric charge. An electrochemical cell is a prime example of DC power. Direct current may flow through a conductor such as a wire, but can also flow through semiconductors, insulators, or even ...
or
alternating current Alternating current (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current (DC) which flows only in one direction. Alternating current is the form in whic ...
is applied between the terminals of the coherer at a predetermined voltage. The mechanism is based on the thin layers of oxide covering all the filings, which is highly resistive. The oxide layers are broken down when a voltage is applied of the right magnitude, causing the coherer to "latch" into its low-resistance state until the voltage is removed and the coherer is physically tapped. The coherer became the basis for radio reception, and remained in widespread use for about ten years, until about 1907. British radio pioneer
Oliver Lodge Sir Oliver Joseph Lodge, (12 June 1851 – 22 August 1940) was a British physicist and writer involved in the development of, and holder of key patents for, radio. He identified electromagnetic radiation independent of Heinrich Rudolf Hertz, H ...
made the coherer into a practical receiver by adding a "decoherer" which tapped the coherer after each reception to dislodge clumped filings, thus restoring the device's sensitivity. It was further developed by
Guglielmo Marconi Guglielmo Giovanni Maria Marconi, 1st Marquis of Marconi (; 25 April 187420 July 1937) was an Italians, Italian inventor and electrical engineering, electrical engineer, known for his creation of a practical radio wave-based Wireless telegrap ...
, then replaced about 1907 by
crystal detector A crystal detector is an obsolete electronic component used in some early 20th century radio receivers that consists of a piece of crystalline mineral which rectifies the alternating current radio signal. It was employed as a detector (demod ...
s. In 1890, Branly demonstrated what he later called the "radio-conductor", which Lodge in 1893 named the
coherer The coherer was a primitive form of radio signal detector used in the first radio receivers during the wireless telegraphy era at the beginning of the 20th century. Its use in radio was based on the 1890 findings of French physicist Édouard Bran ...
, the first sensitive device for detecting radio waves. Shortly after the experiments of
Hertz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
, Dr. Branly discovered that loose metal filings, which in a normal state have a high electrical resistance, lose this resistance in the presence of electric oscillations and become practically conductors of electricity. This Branly showed by placing metal filings in a glass box or tube, and making them part of an ordinary electric circuit. According to the common explanation, when electric waves are set up in the neighborhood of this circuit, electromotive forces are generated in it which appear to bring the filings more closely together, that is, to cohere, and thus their electrical resistance decreases, from which cause this piece of apparatus was termed by Sir
Oliver Lodge Sir Oliver Joseph Lodge, (12 June 1851 – 22 August 1940) was a British physicist and writer involved in the development of, and holder of key patents for, radio. He identified electromagnetic radiation independent of Heinrich Rudolf Hertz, H ...
a coherer. Hence the receiving instrument, which may be a telegraph relay, that normally would not indicate any sign of current from the small battery, can be operated when electric oscillations are set up. Prof. Branly further found that when the filings had once cohered they retained their low resistance until shaken apart, for instance, by tapping on the tube. In ''
On the Changes in Resistance of Bodies under Different Electrical Conditions On, on, or ON may refer to: Arts and entertainment Music * On (band), a solo project of Ken Andrews * ''On'' (EP), a 1993 EP by Aphex Twin * ''On'' (Echobelly album), 1995 * ''On'' (Gary Glitter album), 2001 * ''On'' (Imperial Teen album), 200 ...
'', he described how the electrical circuit was made by means of two narrow strips of copper parallel to the short sides of the rectangular plate, and forming good contact with it by means of screws. When the two copper strips were raised the plate was cut out of the circuit. He also used as conductors fine metallic filings, which he sometimes mixed with insulating liquids. The filings were placed in a tube of glass or
ebonite Ebonite is a brand name for a material generically known as hard rubber, and is obtained via vulcanizing natural rubber for prolonged periods. Ebonite may contain from 25% to 80% sulfur and linseed oil. Its name comes from its intended use as an ...
, and were held between two metal plates. When the electrical circuit, consisting of a
Daniell cell The Daniell cell is a type of electrochemical cell invented in 1836 by John Frederic Daniell, a British chemist and meteorologist, and consists of a copper pot filled with a copper (II) sulfate solution, in which is immersed an unglazed earthenw ...
, a
galvanometer A galvanometer is an electromechanical measuring instrument for electric current. Early galvanometers were uncalibrated, but improved versions, called ammeters, were calibrated and could measure the flow of current more precisely. A galvanom ...
of
high resistance A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active el ...
, and the metallic conductor, consisting of the ebonite plate, and the sheet of copper, or of the tube containing the filings, was completed, only a very small current flowed; but there was a sudden diminution of the resistance which was proved by a large deviation of the
galvanometer A galvanometer is an electromechanical measuring instrument for electric current. Early galvanometers were uncalibrated, but improved versions, called ammeters, were calibrated and could measure the flow of current more precisely. A galvanom ...
needle when one or more electric discharges were produced in the neighbourhood of the circuit. In order to produce these discharges a small Wimshurst influence machine may be used, with or without a condenser, or a
Ruhmkorff coil An induction coil or "spark coil" (archaically known as an inductorium or Ruhmkorff coil after Heinrich Rühmkorff) is a type of electrical transformer used to produce high-voltage pulses from a low-voltage direct current (DC) supply. p.98 T ...
. The action of the electrical discharge diminishes as the distance increases; but he observed it easily, and without taking any special precautions, at a distance of several yards. By using a
Wheatstone bridge A Wheatstone bridge is an electrical circuit used to measure an unknown electrical resistance by balancing two legs of a bridge circuit, one leg of which includes the unknown component. The primary benefit of the circuit is its ability to provid ...
, he observed this action at a distance of 20 yards, although the machine producing the sparks was working in a room separated from the galvanometer and the bridge by three large apartments, and the noise of the sparks was not audible. The changes of resistance were considerable with the conductors described. They varied, for instance, from several millions of ohms to 2000, or even to 100, from 150,000 to 500 ohms, from 50 to 35, and so on. The diminution of resistance was not momentary, and sometimes it was found to remain for twenty-four hours. Another method of making the test was, by connecting the electrodes of a capillary electrometer to the two poles of a Daniell cell with a sulphate of cadmium solution. The displacement of mercury which takes place when the cell is short-circuited, only takes place very slowly when an ebonite plate, covered with a sheet of copper of high resistance, is inserted between one of the poles of the cell, and the corresponding electrode of the electrometer; but when sparks are produced by a machine, the mercury is rapidly thrown into the capillary tube owing to the sudden diminution in the resistance of the plate.Minutes of proceedings, Volume 104 By Institution of Civil Engineers (Great Britain) Branly found that, upon examination of the conditions necessary to produce the phenomena, the following data: * The circuit need not be closed to produce the result. * The passage of an induced current in the body produces a similar effect to that of a spark at a distance. * An induction-coil with two equal lengths of wire was used, a current is sent through the primary while the secondary forms part of a circuit containing the tube with filings and a galvanometer. The two induced currents caused the resistance of the filings to vary. * When working with continuous currents the passage of a strong current lowers the resistance of the body for feeble currents. Summing up, he stated that in all these tests the use of ebonite plates covered with copper or mixtures of copper and tin was less satisfactory than the use of filings; with the plates he was unable to obtain the initial resistance of the body after the action of the spark or of the current, while with the tubes and filings the resistance could be brought back to its normal value by striking a few sharp blows on the support of the tube.


Honours

Branly was nominated thrice for a
Nobel Prize The Nobel Prizes ( ; sv, Nobelpriset ; no, Nobelprisen ) are five separate prizes that, according to Alfred Nobel's will of 1895, are awarded to "those who, during the preceding year, have conferred the greatest benefit to humankind." Alfr ...
, but never received it. In 1911, he was elected to the
French Academy of Sciences The French Academy of Sciences (French: ''Académie des sciences'') is a learned society, founded in 1666 by Louis XIV of France, Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French Scientific me ...
, winning over his rival
Marie Curie Marie Salomea Skłodowska–Curie ( , , ; born Maria Salomea Skłodowska, ; 7 November 1867 – 4 July 1934) was a Polish and naturalized-French physicist and chemist who conducted pioneering research on radioactivity. She was the first ...
. Both had opponents in the Academy: she a female and he a devout catholic, who had left Sorbonne for a chair in the Catholic University of Paris. Branly eventually won the election by two votes. In 1936 he was elected to the
Pontifical Academy of Sciences The Pontifical Academy of Sciences ( it, Pontificia accademia delle scienze, la, Pontificia Academia Scientiarum) is a scientific academy of the Vatican City, established in 1936 by Pope Pius XI. Its aim is to promote the progress of the math ...
. Branly was named as Marconi's inspiration during the first radio communication across the
English Channel The English Channel, "The Sleeve"; nrf, la Maunche, "The Sleeve" (Cotentinais) or ( Jèrriais), (Guernésiais), "The Channel"; br, Mor Breizh, "Sea of Brittany"; cy, Môr Udd, "Lord's Sea"; kw, Mor Bretannek, "British Sea"; nl, Het Kana ...
, when Marconi's message was: "Mr. Marconi sends to Mr. Branly his regards over the Channel through the wireless telegraph, this nice achievement being partly the result of Mr. Branly's remarkable work."Édouard Branly, the Coherer, and the Branly effect - History of Communications
Jean-Marie Dilhac, Communications Magazine, IEEE, Volume: 47 Issue: 9, September 2009, (quoting J. Terrat-Branly, ''Mon père, Édouard Branly'', Corrêa, 1941) accessed 10 May 2011
Branly's discovery of radioconduction was named an IEEE Milestone in Electrical Engineering and Computing in 2010.


Legacy

The quai Branly – a road that runs alongside the River
Seine ) , mouth_location = Le Havre/Honfleur , mouth_coordinates = , mouth_elevation = , progression = , river_system = Seine basin , basin_size = , tributaries_left = Yonne, Loing, Eure, Risle , tributarie ...
in Paris – is named after Branly. It is the name of this road, not of Branly himself, that led to the naming of the Musée du quai Branly. Branly is also commemorated by a technical High School (lycée) in
Châtellerault Châtellerault (; Poitevin-Saintongeais: ''Châteulrô/Chateleràud''; oc, Chastelairaud) is a commune in the Vienne department in the Nouvelle-Aquitaine region in France. It is located in the northeast of the former province Poitou, and the re ...
, a commune in the
Vienne Vienne (; Poitevin-Saintongeais: ''Viéne'') is a landlocked department in the French region of Nouvelle-Aquitaine. It takes its name from the river Vienne. It had a population of 438,435 in 2019.Poitou-Charentes Poitou-Charentes (; oc, Peitau-Charantas; Poitevin-Saintongese: ) is a former administrative region on the southwest coast of France. It is part of the new region Nouvelle-Aquitaine. It comprises four departments: Charente, Charente-Maritime, D ...
region.Lycée Édouard Branly
accessed 10 May 2011


See also

* Musée Édouard Branly, which preserves his laboratory * ''Radio'':
History of radio The early history of radio is the history of technology that produces and uses radio equipment, radio instruments that use radio waves. Within the timeline of radio, many people contributed theory and inventions in what became radio. Radio deve ...
,
Invention of radio The invention of radio communication was preceded by many decades of establishing theoretical underpinnings, discovery and experimental investigation of radio waves, and engineering and technical developments related to their transmission and ...
* ''People'':
Alexander Stepanovich Popov Alexander Stepanovich Popov (sometimes spelled Popoff; russian: Алекса́ндр Степа́нович Попо́в; – ) was a Russian physicist, who was one of the first persons to invent a radio receiving device. declassified 8 Januar ...
,
Karl Ferdinand Braun Karl Ferdinand Braun (; 6 June 1850 – 20 April 1918) was a German electrical engineer, inventor, physicist and Nobel laureate in physics. Braun contributed significantly to the development of radio and television technology: he shared the ...
* : "Receiver for use in wireless telegraphy" Edouard Branly, 1905


References


External links and resources

* Eugenii Katz,
Edouard Eugène Désiré Branly
. The history of electrochemistry, electricity and electronics; Biosensors & Bioelectronics. *

. Robert Appleton Company, ''The Catholic Encyclopedia'', Volume II, 1907. * "

'"". Adventures in Cybersound. * {{DEFAULTSORT:Branly, Edouard Eugene Desire French physicists 1844 births 1940 deaths École Normale Supérieure alumni French Roman Catholics Burials at Père Lachaise Cemetery Members of the French Academy of Sciences Grand Croix of the Légion d'honneur Experimental physicists Radio pioneers