Edouard Branly
Encyclopedia
Édouard Eugène Désiré Branly (23 October 1844 – 24 March 1940) was a French
inventor, physicist
and professor
at the Institut Catholique de Paris
. He is primarily known for his early involvement in wireless telegraphy
and his invention of the Branly coherer
around 1890.
for radio
communication. Branly built upon the discoveries of Temistocle Calzecchi-Onesti
, who demonstrated in experiments in 1884 through 1886 that iron filings
contained in an insulating tube will conduct an electrical current under the action of an electromagnetic wave. The operation of the coherer is based upon the large resistance offered to the passage of electric current by loose metal filings, which decreases under the influence of radio frequency
alternating current
. 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 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
, then replaced about 1907 by crystal detectors.
In 1890, Branly demonstrated what he later called the "radio-conductor," which Lodge in 1893 named the coherer
, the first sensitive device for detecting radio waves. Shortly after the experiments of Hertz, 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 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, 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
, and were held between two metal plates. When the electrical circuit, consisting of a Daniell cell
, a galvanometer
of high resistance, 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
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. 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
, 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.
Branly found that, upon examination of the conditions necessary to produce the phenomena, the following data:
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.
, but he never received it. In 1911 he was elected to the French Academy of Sciences
. His rival was Marie Curie
. Both had opponents in the Academy: she was woman and he was a devout catholic, who left Sorbonne for a chair in the Catholic University of Paris. Finally, Branly won the election by two votes.
Branly was named as Marconi's inspiration during the first radio communication across the English Channel
, 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 died in 1940 and, after a funeral conducted at the Notre Dame cathedral
in Paris and attended by the President of France, Albert Lebrun
, was interred in the Père Lachaise cemetery in Paris.
Branly's discovery of radioconduction was named an IEEE Milestone in Electrical Engineering and Computing in 2010.
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
, a commune in the Vienne
department in the Poitou-Charentes
region.
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
inventor, physicist
Physicist
A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...
and professor
Professor
A professor is a scholarly teacher; the precise meaning of the term varies by country. Literally, professor derives from Latin as a "person who professes" being usually an expert in arts or sciences; a teacher of high rank...
at the Institut Catholique de Paris
Institut Catholique de Paris
The Institut Catholique de Paris, or the Catholic University of Paris, is a private university located in Paris, France. The institute was founded in 1875, under the name Université Catholique de Paris, by Maurice Le Sage d'Hauteroche d'Hulst....
. He is primarily known for his early involvement in wireless telegraphy
Wireless telegraphy
Wireless telegraphy is a historical term used today to apply to early radio telegraph communications techniques and practices, particularly those used during the first three decades of radio before the term radio came into use....
and his invention of the Branly coherer
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 twentieth century. Invented around 1890 by French scientist Édouard Branly, it consisted of a tube or capsule containing two electrodes spaced a...
around 1890.
Biography
The coherer was the first widely used detectorDetector (radio)
A detector is a device that recovers information of interest contained in a modulated wave. The term dates from the early days of radio when all transmissions were in Morse code, and it was only necessary to detect the presence of a radio wave using a device such as a coherer without necessarily...
for radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
communication. Branly built upon the discoveries of Temistocle Calzecchi-Onesti
Temistocle Calzecchi-Onesti
-References:* at radiomarconi.com* at browsebiography.com...
, who demonstrated in experiments in 1884 through 1886 that iron filings
Iron filings
Iron filings are very small pieces of iron that look like a light powder. They are very often used in science demonstrations to show the direction of a magnetic field. Since iron is a ferromagnetic material, a magnetic field induces each particle to become a tiny bar magnet...
contained in an insulating tube will conduct an electrical current under the action of an electromagnetic wave. The operation of the coherer is based upon the large resistance offered to the passage of electric current by loose metal filings, which decreases under the influence of radio frequency
Radio frequency
Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...
alternating current
Alternating current
In alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....
. 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 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 Marconi
Guglielmo Marconi was an Italian inventor, known as the father of long distance radio transmission and for his development of Marconi's law and a radio telegraph system. Marconi is often credited as the inventor of radio, and indeed he shared the 1909 Nobel Prize in Physics with Karl Ferdinand...
, then replaced about 1907 by crystal detectors.
In 1890, Branly demonstrated what he later called the "radio-conductor," which Lodge in 1893 named the coherer
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 twentieth century. Invented around 1890 by French scientist Édouard Branly, it consisted of a tube or capsule containing two electrodes spaced a...
, the first sensitive device for detecting radio waves. Shortly after the experiments of Hertz, 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 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, 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
Ebonite is a brand name for very hard rubber first obtained by Charles Goodyear by vulcanizing rubber for prolonged periods. It is about 30% to 40% sulfur. Its name comes from its intended use as an artificial substitute for ebony wood...
, and were held between two metal plates. When the electrical circuit, consisting of a Daniell cell
Daniell cell
The Daniell cell was invented in 1836 by John Frederic Daniell, a British chemist and meteorologist, and consisted of a copper pot filled with a copper sulfate solution, in which was immersed an unglazed earthenware container filled with sulfuric acid and a zinc electrode...
, a galvanometer
Galvanometer
A galvanometer is a type of ammeter: an instrument for detecting and measuring electric current. It is an analog electromechanical transducer that produces a rotary deflection of some type of pointer in response to electric current flowing through its coil in a magnetic field. .Galvanometers were...
of high resistance, 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
Galvanometer
A galvanometer is a type of ammeter: an instrument for detecting and measuring electric current. It is an analog electromechanical transducer that produces a rotary deflection of some type of pointer in response to electric current flowing through its coil in a magnetic field. .Galvanometers were...
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. 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
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. Its operation is similar to the original potentiometer. It was invented by Samuel Hunter Christie in 1833 and...
, 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.
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 three times nominated for a Nobel prizeNobel Prize
The Nobel Prizes are annual international awards bestowed by Scandinavian committees in recognition of cultural and scientific advances. The will of the Swedish chemist Alfred Nobel, the inventor of dynamite, established the prizes in 1895...
, but he never received it. In 1911 he was elected to the French Academy of Sciences
French Academy of Sciences
The French Academy of Sciences is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French scientific research...
. His rival was Marie Curie
Marie Curie
Marie Skłodowska-Curie was a physicist and chemist famous for her pioneering research on radioactivity. She was the first person honored with two Nobel Prizes—in physics and chemistry...
. Both had opponents in the Academy: she was woman and he was a devout catholic, who left Sorbonne for a chair in the Catholic University of Paris. Finally, Branly won the election by two votes.
Branly was named as Marconi's inspiration during the first radio communication across the English Channel
English Channel
The English Channel , often referred to simply as the Channel, is an arm of the Atlantic Ocean that separates southern England from northern France, and joins the North Sea to the Atlantic. It is about long and varies in width from at its widest to in the Strait of Dover...
, 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 died in 1940 and, after a funeral conducted at the Notre Dame cathedral
Notre Dame de Paris
Notre Dame de Paris , also known as Notre Dame Cathedral, is a Gothic, Roman Catholic cathedral on the eastern half of the Île de la Cité in the fourth arrondissement of Paris, France. It is the cathedral of the Catholic Archdiocese of Paris: that is, it is the church that contains the cathedra of...
in Paris and attended by the President of France, Albert Lebrun
Albert Lebrun
Albert François Lebrun 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 center-right Democratic Republican Alliance .-Biography:...
, was interred in the Père Lachaise cemetery in Paris.
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 SeineSeine
The Seine is a -long river and an important commercial waterway within the Paris Basin in the north of France. It rises at Saint-Seine near Dijon in northeastern France in the Langres plateau, flowing through Paris and into the English Channel at Le Havre . It is navigable by ocean-going vessels...
in Paris
Paris
Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...
– 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
Musée du quai Branly
thumb|225px|Musée du quai BranlyThe Musée du quai Branly , known in English as the Quai Branly Museum, nicknamed MQB, is a museum in Paris, France that features indigenous art, cultures and civilizations from Africa, Asia, Oceania, and the Americas. The museum is located at 37, quai Branly -...
.
Branly is also commemorated by a technical High School (lycée) in Châtellerault
Châtellerault
Châtellerault is a commune in the Vienne department in the Poitou-Charentes region in France.It is located to the north of Poitou, and the residents are called Châtelleraudais.-Geography:...
, a commune in the Vienne
Vienne
Vienne is the northernmost département of the Poitou-Charentes region of France, named after the river Vienne.- Viennese history :Vienne is one of the original 83 departments, established on March 4, 1790 during the French Revolution. It was created from parts of the former provinces of Poitou,...
department in the Poitou-Charentes
Poitou-Charentes
Poitou-Charentes is an administrative region in central western France comprising four departments: Charente, Charente-Maritime, Deux-Sèvres and Vienne. The regional capital is Poitiers.-Politics:The regional council is composed of 56 members...
region.
See also
- Musée Edouard BranlyMusée Edouard BranlyThe Musée Edouard Branly is a museum dedicated to the work of radio pioneer Edouard Branly . It is located in the 6th arrondissement at the Institut Catholique de Paris-ISEP, 21, rue d'Assas, Paris, France, and open by appointment only....
, which preserves his laboratory - RadioRadioRadio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
: History of radioHistory of radioThe early history of radio is the history of technology that produced radio instruments that use radio waves. Within the timeline of radio, many people contributed theory and inventions in what became radio. Radio development began as "wireless telegraphy"...
, Invention of radioInvention Of RadioWithin the history of radio, several people were involved in the invention of radio and there were many key inventions in what became the modern systems of wireless. Radio development began as "wireless telegraphy"... - People: Alexander Stepanovich PopovAlexander Stepanovich PopovAlexander Stepanovich Popov was a Russian physicist who was the first person to demonstrate the practical application of electromagnetic waves....
, Karl Ferdinand BraunKarl Ferdinand BraunKarl Ferdinand Braun was a German inventor, physicist and Nobel laureate in physics. Braun contributed significantly to the development of the radio and television technology: he shared with Guglielmo Marconi the 1909 Nobel Prize in Physics.-Biography:Braun was born in Fulda, Germany, and... - Other: List of people on stamps of France
External links and resources
- Eugenii Katz, "Edouard Eugène Désiré Branly". The history of electrochemistry, electricity and electronics; Biosensors & Bioelectronics.
- "Edouard Branly". Robert Appleton Company, The Catholic Encyclopedia, Volume II, 1907.
- "Edouard Eugène Désiré Branly"". Adventures in Cybersound.