A Flash Back at Elihu Thomson, Founder of the U.S. Electrical Industry

May 03, 2024 by Arjun Nijhawan

Elihu Thomson, a professor-turned-entrepreneur, made several critical discoveries in the field of alternating current (AC), filing more than 700 patents as an inventor. Here’s a look at his life and accomplishments. 

Elihu Thomson, one of the most prolific electrical engineers of the 1900s, made important practical contributions to alternating current (AC) technology and founded the Thomson-Houston Electric Company. This company later merged with Edison General Electric Company to form General Electric, a conglomerate with a market capitalization of over $130 billion today. 


Elihu Thomson

Elihu Thomson. Image used courtesy of NIHF


Thomson, a professor turned entrepreneur, would revolutionize the U.S. electrical industry with key discoveries about electromagnetism.


An Early Aptitude for Science 

Born in Manchester, England, in 1853, Thomson emigrated with his family to Philadelphia at the age of four. Due to work scarcity in England, his parents decided to seek employment opportunities in the United States.

As a child, he showed interest in science and mechanics and applied to enter Central High School at age eleven. He was denied entrance due to his young age, and instead embarked on what some would perhaps now refer to as a “gap year." During that time, his parents allowed him to explore his interests in science independently, and he built a variety of simple telegraph instruments and voltaic cells on his own.

In 1866, Thomson was allowed to enroll in Central High School and graduated several years later. He initially joined a commercial laboratory after graduating but eventually returned to Central High School as an adjunct professor in chemistry. Shortly thereafter, he began to collaborate with fellow professor Edwin J. Houston, forming the beginning of a long partnership in engineering and business. 


Thomson Demonstrates Electromagnetism

By the mid-1800s, the scientific community was extensively investigating the practice and theory of electricity. In 1864, James Clerk Maxwell presented the fundamentals of electromagnetic theory, along with his famous equations, to the Royal Society.  In 1880, Thomas Edison patented the lightbulb, and shortly after, Nikola Tesla invented the induction motor.

Still, many aspects of electromagnetism remained theoretical. Thomas Edison himself did not fully understand some practical implications of electromagnetism and instead believed there was an “etheric force” that transported electricity through the air. Edison even created a contraption known as an etheroscope he believed could channel this force to expand the capabilities of existing telegraphic equipment.


Elihu Thomson’s experiment

Elihu Thomson’s experiment disproved Edison’s hypothesized etheric force. Image used courtesy of PhilSci Archive

Thomson and Edwin Houston, however, conducted an experiment that ultimately disproved the existence of such a force and practically demonstrated electromagnetism. By connecting two batteries to two induction coils wound in opposite directions, Thomson and Houston generated a spark. This spark could also disappear completely based on the arrangement and symmetry of the components of the experiment.

Based on this observation, Thomson and Houston concluded that the electric polarity of charges effectively canceled out, preventing the visible spark seen in some of Edison’s earlier experiments, which he attributed to an etheric force. Edison eventually replicated this experiment himself. Today, we know such phenomena are caused by electromagnetic waves that permeate through space. Over the next decades, Thomson would go on to build and patent numerous electrical components with various practical applications


Thomson: A Prolific Entrepreneur 

While Thomson filed over 700 patents as an inventor, one of his most significant scientific contributions was in electrical welding using alternating current (AC) technology, which was extensively researched and produced by his company, the Thompson Houston Electrical Company. In 1885, Thomson demonstrated electrical welding technology using a lighting circuit connected to copper cable. The metal to be welded was attached to the cable. As current flowed through the cable, so much heat was generated that the metal melted and could be welded together. 

The key to this device was the large coil of wire: a transformer.

Thomson’s electrical welding transformer

Thomson’s electrical welding transformer. Image used courtesy of AllPosters

Transformers can step up or step down voltage. By using a transformer to step down voltage and create a higher current flowing through the lighting circuit, Thomson’s invention leveraged electromagnetism for useful work. In fact, his electrical welder was used to weld train tracks. As Thomson developed a reputation for innovation, he joined American Electric Co. along with only a handful of employees as an “electrician.”


The Rise of AC—and General Electric 

After founding member Frederick Churchill died, American Electric Co. was re-incorporated as the Thomson-Houston Electric Company. Thomson aggressively expanded the business, and by the late 1800s, the company had 4,000 employees and $10M in sales annually.

The company was not without competitors. One of the primary competitors was started by Thomson’s scientific rival, Thomas Edison. While Thomson was a proponent of AC technologies, Edison believed DC was better suited for most practical applications. Over time, however, it became clear that AC was the better choice because of its efficiency; lower current and higher voltages over long distances meant less energy lost due to heat.

In 1892, banker J.P. Morgan acquired both Edison’s company and Thomson’s and merged them into General Electric Company. Today, G.E. is a major conglomerate involved in the manufacturing of a variety of industrial and commercial systems. Elihu Thomson’s innovative mindset lives on not only in the inventions he patented but also in the business he founded.


Thomson's Legacy Echoes Today

Among Thomson's numerous inventions, he was known for the arc-lighting system, a magnetic lightning arrester, an automatically regulated three-coil dynamo, and, of course, a local power transformer. Thomson served as the president of the American Institute of Electrical Engineers AIEE (now the Institute of Electrical and Electronics Engineers (IEEE) from 1889–90. He was the first recipient of the Edison Medal from the organization in 1909. 

Several Ivy Leagues awarded Thomson with honorary degrees for his contribution to the emerging field of electrical engineering: an A.M. from Yale in 1890, a Ph.D. from Tufts College in 1892, and a D.Sc. from Harvard in 1899. He continued to serve in leadership positions to the end of his life, including as a founding member and president of the International Electrotechnical Commission and as the acting president of MIT from 1920–1923.

In Thomson's old age, his wife Clarissa Hovey Thomson reportedly carried a basket with her to contain Thomson's many awards and honors.