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Maxwell Develops the Theory of Electromagnetism

Maxwell Develops the Theory of Electromagnetism

By the middle of the nineteenth century, three great advances in electromagnetic science had occurred. The first was physical. Italian scientist Alessandro Volta’s invention of the battery in 1800 gave researchers a reliable source of electricity with which to conduct experiments. The second was André-Marie Ampère’s theory on the relationship between magnetism and electricity. The third was Michael Faraday’s observation that iron filings followed well-defined lines of force when approached by a magnet. Faraday hypothesized that fields of magnetic and electrical forces exist throughout all space.

James Clerk Maxwell’s studies of electricity and magnetism began in about 1855 and reached fruition after his move to King’s College, London, in 1860. After discovering that the propagation speed of electricity and that of light were identical, he concluded that they were essentially the same phenomenon. He envisioned light as an electromagnetic wave that is propagated through what was then called the “luminiferous aether.” The wave’s oscillations are perpendicular to the line of travel.

Maxwell’s wave and field theory were revolutionary, as they contradicted the existing scientific paradigm. The older view, which went back to Isaac Newton’s mechanics, was that all “action-at-a-distance”—gravity and magnetism, for example—was the result of attraction between particles. Maxwell’s fields provided a competing model of the universe. As such, they were not immediately accepted by other scientists. However, repeated experimental verification during the latter half of the nineteenth century ultimately convinced the scientific community.

Maxwell’s laws can be reduced to a set of four differential equations that describe the behavior of electromagnetic fields and waves. Maxwell first published them in their entirety in 1873 in his Treatise on Electricity and Magnetism. Today, these are known as Maxwell’s equations. They underlie all of modern physics, modern astronomy and cosmology, and most modern technology. Einstein credited the equations as the basis for both the special and general theories of relativity. In fact, the latter is a pure field theory of gravitation. Maxwell’s equations have also resulted in rich findings in particle physics and quantum mechanics.

The notion of an “ether” through which waves travel turned out to be unnecessary to the validity of Maxwell’s equations. There were some contradictions between early twentieth-century experimental results and the equations. These contradictions, one of the mysteries of physics at the time, prompted Einstein to develop his theories of relativity. With the adoption of relativity and the disappearance of “the ether,” Maxwell’s laws became fully consistent with experimental results.


Great Lives from History: Scientists and Science

James Clerk Maxwell

by M. Lee

Scottish physicist, mathematician, and astronomer

James Clerk Maxwell contributed several important scientific findings, particularly in the fields of electromagnetism and thermodynamics. He also predicted the theoretical existence of radio waves before they were produced or observed in the laboratory and is remembered as the first person to discover the true nature of Saturn’s rings.

Born: June 13, 1831; Edinburgh, Scotland

Died: November 5, 1879; Cambridge, England

Primary fields: Physics; astronomy; mathematics

Specialties: Electromagnetism; thermodynamics

Early Life

James Clerk Maxwell was born in Edinburgh, Scotland, on June 13, 1831, into a family of considerable inherited wealth. His father was a lawyer and amateur architect. Maxwell and his family moved to Glenlair when he was two years old. His mother, Frances, took full charge of his education, because the family lived far away from the nearest school he could have attended. She died suddenly of cancer in 1839 when Maxwell was eight years old, and after two years’ worth of limited success with a private tutor, his father decided to send the young Maxwell to Edinburgh Academy in 1841.

Although his initial performance at the academy was not very impressive, it did not take long before Maxwell began showing an ability to comprehend and carry out complex mathematical problems. In fact, he was awarded the top prize in mathematics at his school when he was thirteen years old.

At the age of fourteen, Maxwell wrote a formal scientific paper demonstrating that an ellipse (a type of curved shape that looks like a flattened circle) would always be traced by a pencil attached to a string that is fixed at both ends. He presented this work at a meeting of the Edinburgh Royal Society; his father was a member and Maxwell had begun accompanying him to the society’s sessions to learn from renowned scientists and mathematicians. Among the people he met was physicist William Nicols, whose work excited the young Maxwell and may have been one of the reasons he eventually decided to work in physics himself.

Maxwell entered the University of Edinburgh in November 1847, and he remained at that institution for the next three years, mainly taking courses in science and mathematics. By that time, his future course as a physicist was clear to him, though not to his father, who wanted him to become a lawyer. However, Maxwell demonstrated such a pronounced talent and interest in science—he had published another two Royal Society articles, among other accomplishments—that his father eventually relented.

Life’s Work

In October 1850, when he was nineteen years old, Maxwell transferred to the University of Cambridge to pursue an undergraduate degree in science. His professors immediately noticed Maxwell’s outstanding capability as a scholar. He received exceptional results throughout his undergraduate career and continued to conduct experiments and write papers during this time. He was even elected to the position of scholar at the prestigious Trinity College after two years at Cambridge. When Maxwell graduated in 1854, he was ranked second in his class in mathematics, after taking a difficult and lengthy examination known as the Tripos.

It was at Trinity that Maxwell began working on research dealing with the relationship between magnetism and electricity. He stayed at Trinity for two years, but in 1856, he returned to Scotland and took a position as a lecturer in physics at Marischal College, in the city of Aberdeen. That same year, he was elected to the Royal Society of Edinburgh.

At Marischal, Maxwell turned his attention to astronomy, making a theoretical study of the rings of Saturn. There had been considerable debate in the scientific community about whether the rings were liquid, solid, or something else entirely. Maxwell determined, and it has since been confirmed, that the “rings” were actually tiny particles.

After Marischal College was absorbed into the University of Aberdeen in 1860, Maxwell moved back to England, accepting an offer to teach both physics (then called “natural philosophy”) and astronomy at King’s College in London. He remained at King’s College for five years, during which time he was awarded the Rumford Medal by and elected to the Royal Society. Among the projects he worked on was a study of the nature of optics and the primary colors of light. As a result of this work, he became the first person to produce a color photograph in 1861.

Between 1865 and 1871, Maxwell stepped away from teaching and research, spending six years writing what would become his most important and famous work on magnetism and electricity. He was on the verge of finishing his famous four equations that would encapsulate the entire theory of electromagnetism when he reluctantly returned to the position of professor of experimental physics at Cambridge in 1871. About this time, Maxwell was awarded the Keith Medal from the Royal Society of Edinburgh.

He became the first director of the Cavendish Laboratory and remained there for the next seven years performing administrative duties, continuing to conduct research, and completing the two-volume Treatise on Electricity and Magnetism, which he published in 1873. Having spent two years being treated for stomach cancer, Maxwell died at forty-eight on November 5, 1879, in Cambridge.

Impact

After deducing that Saturn’s rings were composed of tiny particles, Maxwell focused his attention on other substances also composed of tiny particles: the gases found on the Earth. Scientists already understood that gases are made up of small particles called molecules. They also knew that molecules in gases are not at rest, but moving all the time. Physicists were most interested in finding out the process by which molecules moved. Maxwell was one of the early developers of a model known as the kinetic theory of gases.

His greatest finding was the discovery that contrary to the prevailing belief, the molecules of a particular gas do not all travel at the same speed. One of the ideas that led to this discovery was German physicist Rudolf Clausius’s finding that the molecules in a gas are constantly colliding with each other. Maxwell correctly concluded that this changes the speeds of various molecules and devised an equation that could be used to calculate these speeds.

The equation, known as Maxwell’s differential, was a striking development because it was a probabilistic analysis of the problem, meaning that it incorporated the use of statistics to account for the element of chance or randomness in the speeds of molecules. Another of Maxwell’s conclusions was that the movement of molecules in a gas produces heat energy and that if the average speed of the molecules in a gas increases, it causes a corresponding increase in the temperature of the gas. He published Theory of Heat, an influential textbook on this subject, in 1871.

Maxwell’s most significant contribution was his theory of electromagnetism and his four equations that describe how magnetic and electric fields behave and interact with each other. This was an important development in physics because it applied a purely mathematical model for explaining physical phenomena, instead of requiring a mechanical model.

By the time Maxwell began working on electricity and magnetism, it was already known that the two forces were closely related. When an electric field changes, a magnetic field is produced; when a magnetic field changes, an electric field is produced. Maxwell was able to show that not only are the two forces related, but they are actually part of a single force, which is now called electromagnetism. Electromagnetic energy moves through space in the form of waves, which have varying wavelengths (the distance between the top of one wave and the next).

Maxwell correctly concluded that visible light is a type of electromagnetic wave. He also predicted the existence of radio waves, which have a longer wavelength than that of light. The other types of electromagnetic waves include microwaves, infrared light, ultraviolet light, X-rays, and gamma rays.

Further Reading

1 

Campbell, Lewis, and William Garnett. The Life of James Clerk Maxwell. 1882. Charleston: Nabu, 2012. Print. A detailed and accurate nineteenth-century view of Maxwell supplying a full account of his personal life and scientific contributions as they were understood during the 1880s.

2 

Harmon, P. M. The Natural Philosophy of James Clerk Maxwell. New York: Cambridge UP, 2001. Print. An introduction to Maxwell’s physics and worldview, based upon the author’s lecture series.

3 

Mahon, Basil. The Man Who Changed Everything: The Life of James Clerk Maxwell. Chichester: Wiley, 2003. Print. A sympathetic biography describing all of Maxwell’s work in the physical sciences.

4 

Maxwell, James Clerk. The Scientific Letters and Papers of James Clerk Maxwell. 3 vols. Ed. P. M. Harmon. New York: Cambridge UP, 2008. Print. Contains almost all of Maxwell’s correspondence and manuscripts written between 1846 and 1879, including his reference reports to the Royal Society, documents regarding the Cavendish Laboratory, and correspondence with other scientists that document his wide involvement in the scientific community.

Citation Types

Type
Format
MLA 9th
Lee, M. "James Clerk Maxwell." Great Lives from History: Scientists and Science, edited by Joseph L. Spradley, Salem Press, 2012. Salem Online, online.salempress.com/articleDetails.do?articleName=GLSS_0228.
APA 7th
Lee, M. (2012). James Clerk Maxwell. In J. L. Spradley (Ed.), Great Lives from History: Scientists and Science. Salem Press. online.salempress.com.
CMOS 17th
Lee, M. "James Clerk Maxwell." Edited by Joseph L. Spradley. Great Lives from History: Scientists and Science. Hackensack: Salem Press, 2012. Accessed December 14, 2025. online.salempress.com.