Who was Sir John Ambrose Fleming? All About the Father of Electronics

John Ambrose Fleming is renowned as the father of electronics. His contributions to science and engineering have had long lasting effects.
Christopher McFadden
John Ambrose FlemingWikimedia Creative Commons

Sir John Ambrose Fleming is one of the world's most famous and beloved electrical engineers of all time. Fleming made many great contributions to mankind and some groundbreaking innovations in electrical engineering. His two-electrode vacuum-tube rectifier, or diode, would be used for several decades before being replaced with modern transistors. But you might still find one in your home today, perhaps in your microwave!

Heard of the "right-hand-rule"? Then this is the guy you have to thank. Fleming would make further advancements and contributions to electronics, photometry, electric measurements and wireless technology before his passing at the grand old age of 95

Fleming made some remarkable advancements in our understanding of electricity and helped forge the engineering discipline of electronics.

Early life

John Ambrose Fleming was born in Lancaster, England on the 29th of November 1849. Fleming was the eldest of seven children to his father James Fleming and his mother Mary. His father was a Congregational minister.

Despite John being born in Lancaster, his family moved to North London where he would spend most of his life. 

Fleming would begin his academic life at the age of ten when he attended a private school. Here he found he particularly enjoyed geometry.  Before his time at school, his mother had personally tutored him at home.

By the age of ten he had, more or less, learned by rote a book called the "Child's Guide to Knowledge". This was a very popular educational text at the time and one he would even quote in his adult life.

By the age of 11, John Ambrose Fleming knew he wanted to become an engineer. He built his own workshop where he would tinker away building model boats and engines. John even successfully built a basic camera that would spark a lifelong passion for photography.

Work-life balance

His family was not rich so formal training as an engineer seemed out his grasp. Despite this, he was determined to fulfill his desires by supplementing the costs of his education with paid employment. 

Fleming continued his studies at University College School where he enrolled in 1867.  Here he studied under the great mathematician Augustus de Morgan and Physicist George Carey Foster. 

He initially tried to work for a Dublin shipbuilding company but quickly grew tired of tracing drawings. Fleming promptly quit to take up another post as a clerk for a firm on the London Stock Exchange. Fleming kept this position for two years and studied in the evenings. 

Who was Sir John Ambrose Fleming? All About the Father of Electronics
London Stock Exchange circa 1810 Source: Jappalang/Wikimedia  Commons

His labors paid off in 1870 when he graduated with full honors and in the top two of his class.

Fleming, seemingly addicted to higher education, became a student of Chemistry at the Royal College of Science, South Kensington. It was here that he first studied Alessandro Volta's battery. This would become the subject of his first scientific paper. 

The summer of 1874 would see financial troubles force him to look for paid work once again. To fund his education, John took up a position as a science master at Cheltenham College.  


During his "time out," Fleming furthered his own scientific studies. He stayed in continuous contact with James Clerk Maxwell at Cambridge University. Fleming managed to save £400 and also secured an annual £50 grant to cover his costs. With this in hand, he once again enrolled at university but this time at Cambridge in 1877. 

James Clerk Maxwell had predicted that it should be able to make an AC current and send magnetic waves through the air. This was a concept that would busy Fleming for many years to come.

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Here John Ambrose Fleming would be amongst few students who would attend Maxwell's last course of lectures. So few, in fact, that at times he would be the only student in attendance. John would himself admit that Maxwell's lectures were often very hard to follow and understand. It seems Maxwell was not easy to follow, often speaking in a "paradoxical and allusive manner."

Despite this, Fleming graduated once again with a First Class Honours degree in chemistry and physics in 1880, a year after the untimely demise of Maxwell from cancer. 

Who was Sir John Ambrose Fleming? All About the Father of Electronics

James Clerk Maxwell made a big impression on Fleming. Source: GianniG46/Wikimedia commons

Fleming's career kicks into gear

Throughout this time and post-graduation, Fleming lectured at several universities including Cambridge, Nottingham, and University College London between 1885 and 1926. As a professor and chair of the department, he had free reign to conduct his own research. 

Fleming was later awarded the very first title of Professor of Electrical Engineering at University College London.

On the 11th of June, 1887, Fleming married Clara Ripley, who was the daughter of Walter Freake Pratt. Pratt was a solicitor from Bath. Clare died in 1917 and John would later re-marry in 1928 to singer Olive May, the daughter of a Cardiff businessman.

Who was Sir John Ambrose Fleming? All About the Father of Electronics
Fleming's work was instrumental for Marconi's great breakthroughs. Source: Smithsonian Institution/Wikimedia commons

Fleming's time in the industry

John Ambrose Fleming took up a position as an "electrician" at the Edison Electric Light Company in 1882. Here he would advise on lighting systems including the new Ferranti AC system. He would regularly travel to the U.S. over the next decade.

His time with Edison would prove to be very fruitful. Here he was introduced to the so-called Edison effect. It was found that an evacuated light bulb with a second electrode would allow current to flow from one electrode to the other, but only in one direction. While Fleming did not use the idea immediately, he took a keen note of it.

Fleming's great practical knowledge was put to use by various British towns and cities when developing their lighting systems. He would also consult many of the new electric companies like the Swan Lamp Factory and the London National Company. In this capacity, John greatly contributed to the development of electrical generator stations and distribution networks. 

Build it and they will come

Fleming joined the University College London as the Chair of Electrical Technology, the first in England.  He was only supplied with a blackboard and a piece of chalk. It wasn't until 1897 that the Pender Laboratory was founded at the University. Once complete, Fleming took up the position of Pender Chair after the £5000 endowment was in place in honor of John Pender, the founder of Cable and Wireless.

His association with UCL would last for over 40 years. The electrical engineering department he set up there would become famed the world over.

A couple of years later, John became a scientific advisor to the Marconi Company. With Marconi, John would begin working on designs for the power plant at Poldhu, Cornwall. This facility would be instrumental in enabling Marconi to transmit across the Atlantic.

Fleming's "big break"

1904 was probably the most significant year in Flemings life. After tinkering for years, Fleming successfully finalized his designs for a two-electrode vacuum-tube rectifier. His device would build on previous work by his former mentor, James Maxwell. John dubbed it the oscillation valve and he received 16 patents for it. His U.S. patent would later become invalidated because of an apparent "improper disclaimer."


His invention is widely considered to be the true beginning of electronics as this was the first true vacuum tube. This device was used for many decades afterward finding applications in radio receivers, radars, and other devices. It was only superseded 50 years later with the advent of solid-state transistors.

John Ambrose Fleming would later retire from University College London at the age of 77 in 1927. Fleming would be knighted in 1929. He would spend the rest of his life as a powerful advocate for new technology. 

Who was Sir John Ambrose Fleming? All About the Father of Electronics

Fleming prototype valves, 1904

Source: Chetvorno/Wikimedia commons

Fleming's right-hand rule (and left)

As an educator, Fleming would devise many new teaching methods as well as incorporate experimentation and lab work into the classroom. He devised the left and right-hand rules that provided students, even today, with a very simple method of understanding directional relationships between current, magnetic field and electromotive force.

These rules became a handy guide to show the direction of the three parameters of magnetic field, current and electromotive force. Fleming's left-hand rule is generally more applicable to electric motors whilst the right-hand rule more appropriate for electric generators.

It was clear that Fleming thoroughly enjoyed teaching and was a very popular teacher. His students were always impressed with his organization, preparation, and presentation during his lectures. 

Fleming would spend many hours ensuring his demonstrations were clear and, most importantly, actually worked. He would even arrive early before the lecture and expected all his lantern slides to be set out ready for use. Nothing was to go wrong!

He would continue teaching students at UCL until he finally retired in 1926.

Inventions and contributions to the world

Fleming made significant advancements in our understanding and application of electricity. Early in his career, Fleming would work tirelessly investigating photometry, working with high voltage AC currents and design some of the first electric lighting for shipping. 

John Ambrose Fleming is also known for his invention of the thermionic valve. This device is also known as the two-electrode radio rectifier, vacuum diode, kenotron, thermionic tube and of course the Fleming valve. 

Who was Sir John Ambrose Fleming? All About the Father of Electronics

Memorial plaque to John Fleming 9 Clifton Gardens, Maida Vale, London

Source: Spudgun67/Wikimedia commons

During his tenure at UCL, he undertook a lot of research. His first ten years at UCL were spent focussing on refining the theory behind transformers. Low voltage testing was conducted at UCL with the majority of "field trials" were carried out at a substation owned by the London Electric Supply Corporation.

The great successes of his research were presented to the Institution of Electrical Engineers in 1892. His work represented a landmark in the understanding of transformer theory. Overnight he became a leading authority on transformers and was recognised for his work improving the accuracy of AC measurements.

Fleming also penned more than a hundred scientific papers and books. Notable amongst his back catalogue included the highly influential "The Principles of Electric Wave Telegraphy" published in 1906

He also wrote and published "The Propagation of Electric Currents in Telephone and Telegraph Conductors" in 1911. 

For his contributions to science, John was knighted in 1929.

Fleming's tube

John Ambrose Fleming's tube was the first of its kind in the world when he filed for a U.S. patent in 1905. His device was a high-vacuum diode that was used as a rectifier in many appliances at the time. These ranged from X-Ray equipment to electrostatic precipitators where high voltage and low currents are needed.

Its impact was immediate and lasting contribution to the field of electronics undeniable. As impressive as his device was, it was about to be upgraded by one American engineer Lee DeForest a couple of years later. 

DeForest took Fleming's idea and added an extra electrode to form a grid.


Who was Sir John Ambrose Fleming? All About the Father of Electronics

Flemings US Patent.

Source: United States Patent Office/Wikimedia commons

This new "triode" would cause an uproar amongst the scientific community. Most felt that this new device was a gross infringement on Fleming's invention. Without delay, John began a series of lawsuits against DeForest for patent infringement. Though they would ultimately fail, Fleming would forever be known as the original inventor. 

Fleming's valve would have a long an illustrious influence for at least three decades. It was ultimately replaced by the transistor but was an integral part of early televisions, telephones and even some early computers and many other devices. 

Who was Sir John Ambrose Fleming? All About the Father of Electronics

DeForest's Audion or triode vacuum tube, 1906

Source: Chetvorno/Wikimedia commons

Fleming was an anti-evolution activist

In 1932, Fleming, as well as Douglas Dewar and Bernard Acworth, actually helped form the Evolution Protest Movement. This British Creationist organization was, by all accounts, "the oldest creationist movement in the world". It still exists to this day as a registered charity. 

The movement actually has its origins in the Victoria Institute (Philosophical Society of Great Britain). The Victoria Institute's stated objective was to defend "the great truths revealed in Holy Scripture ... against the opposition of Science falsely so called."

Although officially it didn't oppose evolution it none the less attracted many scientists skeptical of Darwinism. Its heyday was during the late 19th Century but by 1910 or so its popularity had largely been culled. 

Who was Sir John Ambrose Fleming? All About the Father of Electronics
Bernard Acworth was an important force as well as Fleming in the movement Source: creation

Celebrated submariner and free-lance journalist Bernard Acworth proposed the foundation of the Evolution Protest Movement in 1932. Its mission statement was to restrict itself "as far as that might be possible, to the scientific rather than to the philosophic and religious plane". It existed only on paper until around 1935 when it was officially publically launched.

Despite various media campaigns and some growth in membership throughout the 1930's through to the 1950's, it failed to win the support of C.S. Lewis who was a prominent Christian Apologist at this time.

The movement would continue to grow throughout the 1960's through to the present day. The organization was rebranded the Creation Science Movement in 1980. Its current chairman, David Rosevear Ph.D. used to actually be a senior lecturer in chemistry at Portsmouth University. 

Who was Sir John Ambrose Fleming? All About the Father of Electronics
Genesis Exposition mock grave display Source: geni/Wikimedia commons

A very busy retirement

Fleming's later years were dogged by his loss of hearing. Despite it, he continued to tinker away with his interests and hobbies. John Ambrose Fleming was an early supporter of new technology, especially children television programmes. He even became the President of the Television Society of London in 1926.

John Fleming would continue to keep his "finger on the pulse", as much as he could. He would often be seen addressing the Physical Society of London, the last time in his late eighties, and would continue to write. Fleming would add his Memories of a Scientific Life to his existing extensive portfolio of work. 

His other passions included mountain climbing, watercolor painting and of course photography. John was also a devout Christian. His preaching skills were said to be second to none. John was even invited to deliver a sermon at St. Martin's in the fields in central London.

Who was Sir John Ambrose Fleming? All About the Father of Electronics

John Ambrose Fleming's residence at 9 Clifton Gardens, Maida Vale, London. Source: Spudgun67/wiki commons

Death and legacy

Fleming died at his home in Sidmouth, Devon in 1945. He was 95 years old

John Ambrose Fleming died childlessly. The majority of his estate was left to Christian charities, especially those that focussed their attention on the poor. 

Fleming's honors in life were numerous, as you would expect. Amongst these was the highest distinction of the Royal Society of Arts. He also received the Gold Albert Medal in 1921, the Institution of Electrical Engineers' Faraday Medal in 1928, and the Institute of Radio Engineers' Gold Medal in 1933.

Also in 1933, John was awarded the IRE Medal of Honor for "the conspicuous part he played in introducing physical and engineering principles into the radio art".

Who was Sir John Ambrose Fleming? All About the Father of Electronics

The transistor was invented two years after Fleming's death. Source: 101science

Fleming was honored by the London Power Company in 1941 when they named the new coastal collier the SS Ambrose Fleming.

His contributions to electronics, especially in communications and radar, were vitally important to the allied war effort during the Second World War. 

In 2004, John Ambrose Fleming was further honored with a Blue Plaque presented by the Institute of Physics was revealed at the Norman Lockyer Observatory in Sidmouth. The plaque was to commemorate the centenary of the invention of the Thermionic Radio Valve.

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