An occasionally used English adjective

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1 ARTICLE JOHN AMBROSE FLEMING AND THE CENTENARY OF A NOBEL PRIZE IN SCIENCE IT IS THE TRIFLES THAT COUNT BHUPATI CHAKRABARTI* An occasionally used English adjective ambidextrous describes a person whose both hands can work with equal agility. In Mahabharata Arjuna was designated as one with that ability. And from our experience we know that it is easier to designate someone either as right handed or as left handed but not with that adjective. But in the field of Physics we have at least one very well known ambidextrous person. Students learn about his left hand rule when the principle of an electric motor is explained to them and then they find that the same scientist rules with his right hand when it comes to explaining of the principle of an electric generator or dynamo. The man responsible for these, John Ambrose Fleming was born one hundred and sixty years ago in And he was really an ambidextrous scientist who contributed both in theoretical and applied physics with equal aplomb. Not only for his two rules those go by his name but for his immense contributions in the field of radio transmission and radio telegraphy in an active career that spanned for nearly seventy five years. It began in the last quarter of the nineteenth century and continued to the first half of the twentieth century. And probably his most famous and of course most useful invention that has completed a century of its existence a few years back is the diode valve. With the electronics ruling the roost of the technological innovations that we come across in today s world this is possibly right time that we look back to this first electronic device and its colourful inventor Sir John Ambrose Fleming. Moreover this year, 2009 marks the centenary year of the Physics Nobel Prize that went to Marconi and Karl Fardinand Braun for their development of wireless telegraphy. This was a work * Department of Physics, City College, Kolkata bhupati2005@yahoo.co.in where Fleming had a role and this was the Prize that we did talk about a lot last year during the celebration of 150 th birth anniversary of Sir J.C. Bose for the reasons well known. The valve came to be known as Fleming valve and now we call it a diode valve while the Americans call it a vacuum tube. It was in 1904 the British Engineer Fleming was working as a consultant to Marconi, the Italian physicist who was at that time took up the responsibility of establishing trans-atlantic telegraphy. They were actually looking for a receiver for the radio waves and Fleming was deeply involved in the work. Since Fleming 112 SCIENCE AND CULTURE, MARCH-APRIL, 2010

2 also worked earlier as a consultant with Thomas Alva Edison who discovered thermionic emission in 1883 he was aware of the effect known as Edison effect after the name of its discoverer. That definitely helped Fleming to patent his, nay the mankind s first electronic device back in And it was a relatively crude form of what is now known as a diode valve. He took patent of this invention in the same year i.e. in 1904 and that invention was came to be known as Fleming valve. The one-way conduction, better known as rectification was actually discovered by Karl Ferdinand Braun ( ) in He first found that metal wire contacts on lead sulphide or galena crystals shows very high resistance when current is sent through in one direction while the other direction offers much smaller resistance. Braun persisted with the research in the field and developed what is known as crystal detector that he introduced as a part of the wireless detector. In has to be noted that the name of Italian scientist Marconi appeared in all media and in a large number of conferences and seminars last year (2008) when the world observed the 150th birth anniversary of Sir J.C. Bose. Marconi was not only inspired by the ideas of Sir J.C. Bose on the wireless communication by millimeter waves, he closely followed the works of Hertz, Oliver Lodge and others. He actually took special interest in the subject rightly gauging the commercial prospect of wireless communication for which scientists, technologists and of course entrepreneurs were putting up efforts right from the middle of nineteenth century. Marconi was guided by Fleming in a big way to achieve the reliable transatlantic wireless communication. Moreover Fardinand Braun s work was there to pave the way for first trans-atlantic wireless communication. Fleming was senior to Marconi by about 25 years and in early 20 th century Fleming was an established professor of Electrical engineering. In 1909, exactly 100 years back when Marconi won the Nobel Prize in Physics, he actually shared it with Karl Ferdinand Braun but Fleming was not there in the winner s list. It did hurt Fleming. The winning of Nobel Prize was in a way was very special for Marconi as he was possibly the first industrial physicist to get that recognition. He was not affiliated to any academic institution at that time. Rather Fleming diode valves, VOL. 75, NOS

3 he had his own company and the work he undertook was actually part of his commercial venture. He was, in today s parlance an entrepreneur par excellence that floated a company in his name, took patents of his work and was quick enough to shift his base from Italy to England just to pursue his goal of achieving the wireless communication across the Atlantic. Oscillation valves first employed by Fleming in October, 1904 An early model of a Fleming diode valve, 1905 The Fleming oscillation valve, ca It is not easy to quantify one single person s contribution in a particular scientific or technological breakthrough yet it is now acknowledged that Marconi got the inspiration of his work from Sir J.C. Bose while Fleming was among the leaders who saw the execution of the project that may be termed as the trans-atlantic wireless communication. Sir J.C. Bose left the research field of wireless communication well before 1909 and could appreciate Marconi s achievement in his writings. But Fleming still very much involved in teaching and research in engineering possibly a bit upset as the Nobel Prize also eluded him. Fleming was indeed a very interesting personality. He was a student of Maxwell in 1877 under whom he studied electricity and magnetism at Cambridge. The subject proved to be extremely interesting for young Fleming and he completed his D.Sc. under the great physicist Maxwell who had a very untimely demise in 1879 only at the age of forty-eight. But this brief association with Maxwell kept a deep imprint in the future career of Fleming who developed his lifelong interest for electricity and the related instrumentation. It was the infancy of electric lighting though it was gaining popularity. Fleming in 1881 joined the electric company founded by Edison as a consultant that he continued for next ten years and began to develop different equipment and accessories for electric lighting. This served two basic purposes, one the electric lighting become gradually popular and Fleming came out with a number of important inventions in the field of photometry. The way Fleming worked both at the industry as well as in the academic institution is quite remarkable considering his time. Fleming actually had a keen interest in the subject of electrical engineering. But as one can understand that without the emergence of electricity as a viable and attractive component of our daily life the subject of electrical engineering cannot emerge. That is why Fleming was doing next best option available i.e. Physics. He however had an excellent flare for delivering good quality lecture and he did so in the University College of London (UCL) on his favourite topics related to electricity and its different aspects. Finally in 1885 the UCL asked him to build up a department with Fleming as the professor. It 114 SCIENCE AND CULTURE, MARCH-APRIL, 2010

4 Fleming joined the company of Marconi as a consultant in 1899 while he was a professor at UCL. At that time Marconi was trying hard to send transatlantic wireless signals that he finally succeeded in 1901 and now we know it was possible for the existence of ionosphere in the upper atmosphere till unknown at that time. But this signal was not detectable or could be converted into speech, as there was no suitable detector. Fleming while addressing this problem actually came up with the invention of the diode valve. He was a keen observer of the phenomena that used to take place during an experiment conducted in the laboratory. He used to make it a point to look at every small thing critically with the eye of an inventor. The background for this invention is even better expressed in his own words, that shows how as an experimentalist he used to take critical look at the happenings at the laboratory. He said In 1882, as electrical adviser of the Edison Electric Light Company of London, I was brought into close touch with the many problems of incandescent lamps and I began to study the was a job indeed close to his heart and he did it with a great success and continued in his position for the next forty years. An experimental lamp which John Ambrose Fleming used Part of the patent drawing of the first wireless detector to use a thermionic valve, 1904 VOL. 75, NOS

5 physical phenomena with all the scientific means at my disposal. Like everyone else, I noticed that the filaments broke easily at the slightest shock, and when the lamps burned out the glass bulbs became discolored. This discoloration of the glass was generally accepted as a matter of course. It seemed too trifling to notice. But in science it is the trifles that count. The little things of today may develop into the great things of tomorrow. Wondering why the glass bulb grew dark, I started to investigate the matter, and discovered that in many burned-out lamps there was a line of glass that was not discolored. It was as though someone took a smoked glass, drew a finger down it, and left a perfectly clean line behind. I found that the lamps with these strange, sharply defined clean spaces were covered elsewhere with a deposit of carbon or metal, and that the clean line was immediately in the plane of the hairpin-shaped carbon filament and on the side of the loop opposite to the burned-out point of the filament. It was obvious to me that the unbroken part of the filament acted as a screen to that particular line of clear glass, and that the discharge from the overheated point on the filament bombarded the remainder of the bulb with molecules of carbon or vaporized metal shot out in straight lines. My experiments at the end of 1882 and early in 1883 proved that I was right. Interestingly there was much debate regarding the wavelength of the first transatlantic signal that Marconi sent in Fleming made it clear that his detector did not existed at that time and he did not know the exact wavelength. In his own language The wavelength of the electric waves sent out from Poldhu Marconi station in 1901 was not measured because I did not invent my cynometer or wavemeter until October, The height of the original aerial (1901) was 200 feet, but then there was a coil of a transformer or jiggeroo as we called it in series with it. My estimate was that the original wavelength must have been not less than about 3,000 feet, but it was considerably lengthened later on. I knew at that time that the diffraction or bending of the rays around the earth would be increased by increasing the wavelength and after the first success I was continually urging Marconi to lengthen the wavelength, and that was done when commercial transmission began. I remember I designed special cymometers to measure up to 20,000 feet or so. Fleming retired from University College of London post in 1926 when he was more than seventy-five years old. Till that age he was an active researcher. He passed his last days at Devon but liked to visit London in connection with different work at Royal Society, Television Society and other organizations. Fleming had a long life span and passed away in 1945, when he was ninety-six years old. By that time the World War II was over. Not only the wireless communication but also the television transmission has turned into a reality by that time. In fact on the verge of his centenary year a new era started with the legacy of John Ambrose Fleming. It was Three scientists and engineers Shockley, Brittain and Bardeen in Bell laboratories in USA invented the transistor, the semiconductor device that can amplify a signal. And a new phase started about which all of us know. And all of us live in the midst of that. The diode scheme This is the simplest type of valve, having just two electrodes anode and cathode (filament in the case of battery valves, as shown in the diagram). The electrodes are enclosed within an evacuated envelope bulb of glass, the connections to the electrodes passing through this envelope via airtight seals. The hot filament or cathode generates an invisible cloud of electrons in the space around it. A positive potential on the anode attracts these and a current flows from cathode to anode. The air is removed in order to allow free movement of the electrons as they pass from cathode (filament) to anode. References Materials for this write up has been drawn from different websites given below 1. The centenary of diode valve (University College of London, Department of Electronic and Electrical Engineering) A report in pdf 2. John Ambrose Fleming (The wikipedia article) [ (Photographs have mainly been taken from here) 116 SCIENCE AND CULTURE, MARCH-APRIL, 2010