Historical Engineers: John Ambrose Fleming and the First Vacuum Tube

July 18, 2020 by Vanessa Samuel

Regarded the father of modern electronics, John Ambrose Flemings created the first vacuum tube while also providing some helpful educational tips now used in engineering education.

Some of the touchstone electronic technology today—from radios and early TV sets to computers—was made possible, in part, to John Ambrose Fleming

Fleming was an English physicist and engineer from the late-19th to mid-20th centuries. Growing up, Fleming had an aptitude for math and science and worked many jobs to pay his way through the University College of London to study math and physics. During his post-grad years, he began studying electrical engineering at St. John’s College at Cambridge, where he worked closely with his professor James Clerk Maxwell.


John Ambrose Fleming in 1906

John Ambrose Fleming in 1906. Image used courtesy of Wikimedia Commons

Fleming is best known for his invention of the vacuum tube and the commonly used right-hand rule in electromagnetism. How exactly did Fleming devise the vacuum tube? And how has his work impacted the field of electrical engineering today? 


Fleming Draws Inspiration from the Edison Effect

In a centenary tribute to Fleming's patent of the thermionic diode, Jefferson Labs explains the origin story of Fleming's discovery (PDF).

Fleming learned much from Maxwell about electricity and magnetism. While working at the Edison Telephone and Electric Light Company in England, Fleming had the opportunity to visit the United States and work with Thomas Edison and learn about something called the Edison effect.

Edison noticed that when another electrode was placed near filament, there was current in the filament. On the additional electrode/plate, electrons were traveling from the heated filament to the cooler plate.

Later, when Fleming was working as a scientific advisor for Guglielmo Marconi’s company, he combined his knowledge of the Edison effect with the discoveries of the electron by J.J. Thomson to create the first electronic rectifier, also known as the vacuum tube. You learn more details on early tube history in the All About Circuits textbook.


The Impact of the Vacuum Tube

Fleming's vacuum tube was able to convert AC to DC. The DC signal was able to be picked up by a radio or telephone receiver, laying the groundwork for wireless technology and other electronics (considering transistors were developed after Fleming’s vacuum tube).


The Fleming valve

The Fleming valve was the first thermionic diode and the first vacuum tube. Image used courtesy of Wikimedia Commons

Fleming's rectifier made radio more efficient than before and even helped to transmit the first set of radio waves across the Atlantic ocean. Fleming’s tube was later used in TV sets and electronic computers as they became more prominent. Now, even electric guitar amplifiers use Fleming’s vacuum tube technology. 


The Right-Hand Rule: a Long-Standing Teaching Tool

While Fleming's most heralded accomplishment was the first thermionic diode and vacuum tube, he also made his mark on engineering education.

John Fleming had an extensive career as a professor and was the first chair of electrical engineering at England’s University College. As a professor, Fleming developed the right-hand rule to help his students understand the relationship between current magnetic field and electromotive force. 

In the right-hand rule, the thumb points in the direction of the force of the conductor relative to the magnetic field. The pointer finger represents the direction of the magnetic field. And finally, the second finger displays the direction of the current that is generated within the inductor.


Visual of the right-hand rule

Visual of the right-hand rule. Image used courtesy of Douglas Morrison by [CC BY-SA 3.0]


This rule is widely used today in physics and engineering classes to understand electromagnetism, specifically when a conductor is brought under a magnetic field to show the induced current. 


The Father of Modern Electronics

John Ambrose Fleming's invention of the vacuum tube heavily influenced modern-day electronics and reshaped telecommunications. His right-hand rule is taught globally to those learning about electromagnetism. Like one of his mentors, James Clerk Maxwell, Fleming's work has had a ripple effect on the lives of EEs today. 



In what ways have Fleming's now-foundational findings affected your work? We're interested to hear your experience. Also, if you have a historical engineer you'd to see covered, let us know in the comments below.