John Ambrose Fleming was a British physicist and electrical engineer. He was also professor of electrical engineering at University College London.
Background
John Ambrose Fleming was born on November 29, 1849, in Lancaster, England. He was the eldest of seven children born to James Fleming, a Congregational minister, and his wife Mary Ann, the daughter of John Bazley White, a trailblazer in Portland cement manufacturing. In 1854, Fleming's father took a post at the Kentish Town Congregational Chapel and moved the family to North London.
Education
Fleming was educated at Lancaster Royal Grammar School, University College School, London, and then University College London, where he received his Bachelor of Science degree in 1870. He entered St John's College, Cambridge in 1877, gaining his Bachelor of Arts in 1881.
After a period of alternate science teaching and additional study, John entered Cambridge University in 1877 to work under James Clerk Maxwell in the new Cavendish Laboratory. There he helped to repeat the century-old electrical experimerits of Henry Cavendish, whose notes on them had recently come to light. Fleming was made demonstrator in 1880, and in the following year he became professor of physics and mathematics in the newly constituted University College at Nottingham.
He resigned after a year to become a consultant to the Edison Electric Light Co. in London. In 1885 he was appointed professor of electrical technology at University College, a post he held for forty-one years. He made many contributions to the design of transformers, to the understanding of the properties of materials at liquid-air temperatures, to photometry, and to electrical measurements in general. He was an outstanding teacher; the right-hand rule (a mnemonic aid relating direction of magnetic field, conductor motion, and the induced electromotive force) is attributed to him. He was also a highly successful popular scientific lecturer.
At University College he experimented widely with wireless telegraphy and gave special courses on the subject. He was aware of Edison’s observation of the “Edison effect” of unilateral flow of particles from negative to positive electrode, and he repeated some of the experiments, with both direct and alternating currents, beginning in 1889. During the following years, he cooperated with Marconi in many of his experiments and helped to design the transmitter employed by Marconi in spanning the Atlantic in 1901. Thus it was not until 1904 that he returned to his experiments on the Edison effect, with a view to producing a rectifier that would replace the inadequate detectors then used in radiotelegraphy. He named the resulting device a “thermionic valve,” for which he obtained a patent in 1904. This was the first electron tube, the diode, ancestor of the triode and the other multielectrode tubes which have played such an important role in both telecommunications and scientific instrumentation.
Fleming led an incredibly active scientific life. He read the first paper ever presented to the Physical Society on its foundation in 1874 and read his last paper to the same body sixty-five years later, in 1939. His career covered the time from Maxwell to the advent of electronic television. He published more than a hundred important papers. He became professor emeritus after his retirement in 1926 but continued to be scientifically active nearly until his death at the age of ninety-five.
On 11 June 1887 John married Clara Ripley, daughter of Walter Freake Pratt, a solicitor from Bath. She died in 1917. On 27 July 1928 he married the popular young singer Olive May Franks, of Bristol, daughter of George Franks, a Cardiff businessman. He had no children.