History of electricity

by Chris Woodford. Last updated: December 3, 2021.

If the future's electric, why isn't the past? Think a little bit about that simple-sounding question and you'll understand what science is all about and why it matters so much to humankind. Consider this: the ancient Greeks knew some basic things about electricity over 2500 years ago, yet they didn't have electric cookers or fridges, computers or vacuum cleaners. How come?

Electricity is just the same as it was back then: it works in exactly the same way. What's changed is that we understand how it works now and we've figured out effective ways to use it for our own ends. In other words, science (how we understand the world) has gradually helped us to produce effective technology (how we harness scientific ideas for human benefit). The steadily advancing science of electricity has led to all kinds of electrical technologies that we can no longer live without. It's been an incredible achievement, but where and how did it begin? Let's take a closer look!

Photo: A statue of Thales of Miletus gripping the discovery for which he's best known: electricity. Photo of a statue by Louis St. Gaudens at Union Station, Washington, DC. Credit: Photographs in the Carol M. Highsmith Archive, courtesy of Library of Congress, Prints and Photographs Division.

Ancient sparks

Science historians have charted human knowledge of magnetism as far back as 2637BCE, which seems to be the date when compasses were used for the first time. [1] Archeologists have found indications that primitive, perhaps "accidental" electroplating (coating one metal with another) dated back almost as long, but the scientific history of electricity is much more recent. [2]

Way back in 600BCE, a Greek mathematician and philosopher named Thales (c.624–546BCE), who lived in the city of Miletus (now in Turkey), kicked off our story when he discovered the basic principle of static electricity (electricity that builds up in one place). As he rubbed a rod made of amber (a fossilized tree resin), he found he could use it to pick up other light objects, such as bits of feathers. (You've probably done a similar experiment rubbing a ruler or a balloon and using it to pick up pieces of paper.)

Before Thales came along, people might well have explained something like this as magic: ancient people didn't reason things out scientifically the way we do today. Their explanations were often a muddled mixture of magic, superstition, folklore (stories), and religion. [3] Thales is often called the world's first scientist, because he was one of the very first people who tried to find sensible, rational explanations for things. His explanations weren't always correct (he thought everything in the Universe was ultimately made of water and believed Earth was a flat disc), but they were the best logical deductions he could make from his observations of the world—and, in that sense, they were scientific. [4]

Photo: "Aristotle" pictured at the National Academy of Sciences, Washington, D.C. Credit: Photographs in the Carol M. Highsmith Archive, courtesy of Library of Congress, Prints and Photographs Division.

The logical, scientific ways of doing things we rely on today were developed by later Greeks such as Aristotle (348–322BCE) and Archimedes (287–212BCE), who built on Thales' work, and Islamic scholars such as Alhazen (965–1040CE), who gave us the scientific method: coming up with a tentative explanation for something (a hypothesis), which is then tested through experiments to make a more robust explanation (a theory). Important though these people were, electricity (as we know it today) didn't figure in their thinking. They had little conception of how useful it could be—or what it would eventually lead to. They were more concerned with astronomy, mathematics, matter, and optics (how light works). Science might have been in its advent, but electricity was still just a "magical" curiosity—of very little practical use.

Positive and negative

Artwork: William Gilbert gave us our word for "electricity." Photograph courtesy of the Wellcome Collection published under a Creative Commons Attribution 4.0 International (CC BY 4.0) licence.

Incredibly, the scientific study of electricity didn't really advance any further for a full 2000 years after Thales' original discovery. But around 1600CE, Englishman William Gilbert (1544–1603), a physician to the English Queen Elizabeth I, started to probe it further. Gilbert was the person who coined the Latin term "electricus" (a word meaning "like amber," reflecting Thales' original discovery) and he believed electricity was caused by a fluid called "effluvium" that could move from place to place. This was an important insight because it was the first real suggestion that electricity could form what we now call a current, as well as remain static (in one place). Although Gilbert is much better known for his work on magnetism (he made the important deduction that Earth behaves like a giant magnet), and compared it with electricity, he didn't unite the two things in a single theory. If he'd done so, he probably would have gone down in history as one of the greatest physicists of all time. (As we'll see later, the person who finally achieved that, James Clerk Maxwell, is celebrated in exactly that way.)

Artwork: "Experiments and Observations Tending to Illustrate the Nature and Properties of Electricity": The cover of William Watson's book of electrical research.

It was now becoming clear that there was much more to electricity than the ancients had realized. In 1733/4, almost 150 years after Gilbert's death, a French physicist named Charles du Fay (1698–1739) made the next important breakthrough when his experiments revealed that static electricity could come in two different (opposite) flavors, which he named "vitreous" and "resinous." If you rubbed some objects, they gained one kind of electricity; if you rubbed others, they gained the opposite kind. Just as two "like" magnets (two north poles or two south poles) will repel, so two objects with "like charges" of electricity will also repel, while objects with unlike charges (like magnets of opposite poles) will attract.

Although we now know this idea is correct, back in the 18th century, such a convoluted explanation sounded wrong to some people. Why should there be two kinds of electricity? Didn't it flout a basic scientific principle called Occam's razor—the idea that explanations should be as simple as possible?

Englishman Sir William Watson (1715–1787) thought there was just one kind of electricity, with an ingenious explanation much more like our modern view: if we have too much electric charge, it seems like one kind of electricity; if too little, the other kind. Watson gave us the concept of electric circuits (closed paths around which charge flows) and made an important distinction between conductors and insulators. He was also one of the first to show that electricity could zip down very long wires, and his other experiments included passing electricity through lines of several people to give them surprising electric shocks.

Photo: A museum exhibit at Independence National Historical Park in Philadelphia, Pennsylvania, illustrating Benjamin Franklin's highly dangerous attempt to catch electricity in a thunderstorm. Credit: Carol M. Highsmith's America Project in the Carol M. Highsmith Archive, courtesy of Library of Congress, Prints and Photographs Division.

Two decades later, the question of how many kinds of electricity there were was effectively settled by Watson's contemporary, the American polymath Benjamin Franklin (1706–1790). Printer, journalist, inventor, statesman, scientist and more, he made all sorts of contributions to 18th-century American life. One of his most important achievements was confirming that there was a single "electric fluid," giving rise to the two "kinds" of electricity, which he named (as we still do today) "positive" and "negative." Like Watson, Franklin helped to tease out the mystery between static and current electricity. In his most famous (and indeed most dangerous) experiment, he flew a kite in a thunderstorm with a metal key attached to it by a long string. The basic idea was to catch electrical energy in the clouds (static electricity) from a lightning strike (current electricity), which he hoped would travel down the string to the key (more current electricity). Fortunately, lightning didn't strike the kite, which might well have killed Franklin, but he was able to detect charges and sparks, so confirming his ideas. DON'T try anything like this at home! [5]

Franklin's electrical research marked a new milestone and hinted of much more to come, because it suggested electricity could be captured and stored as a form of energy. But electricity turned out to be even more useful when people discovered how it could exert a force. That was demonstrated by Frenchman Charles Augustin de Coulomb (1736–1806), who charged up two small spheres with positive electricity and then measured the (repulsive) force as they pushed away from one another (repelling the same way as two magnets with like charges). Coulomb found that the force between charges depended not just on their size but also on the distance between them—something now known as Coulomb's law. (The basic unit of electric charge is also named the Coulomb in his honor.)

Electrical experiments were still hampered by the sheer difficulty of making and storing electricity, which, at this time, essentially relied on rubbing things to build up a good static charge. The study of electricity really advanced when a group of European scientists devised ways of storing electrical charges in glass jars with separate pieces of metal attached to the inside and outside surfaces—devices known as Leyden jars, which were the first effective capacitors (charge-storing devices). Developed independently in the 1740s by German Ewald Georg von Kleist and Pieter van Musschenbroek (of the city of Leyden, hence the name), they offered a much more convenient way of studying electricity.

Photo: Electrical research as it was in the early 18th century: A pair of glass Leyden jars (center) with their electrical connections to an electricity generating machine (right). Oil painting by Paul Lelong c.1820 courtesy of the Wellcome Collection published under a Creative Commons Attribution 4.0 International (CC BY 4.0) licence.

Animal magic

Ever since Thales' original discovery, scientists knew that static electricity could be made by rubbing things, but no-one knew exactly why this was so or where the electricity ultimately came from. In the late 18th century, Italian biologist Luigi Galvani (1737–1798) found he could make electricity in a completely different—and totally unexpected—way: using the legs of a dead frog. In his most famous experiment of all, when he pushed brass hooks into a frog's legs and hung them from an iron post, he saw the legs twitch from time to time as electricity flowed through them. That led him to think that living things like frogs contained something he called "animal electricity," which the metals were somehow releasing.

Artwork: Luigi Galvani believed he'd discovered "animal electricity" when he hung a frog's legs from a metal hook (left) and watched them twitching. Illustration courtesy of US Library of Congress.

In fact, as another Italian, physicist Alessandro Volta (1745–1827) soon discovered, Galvani had leaped to the wrong conclusion. The twitching frog was merely the current detector, not the source of the current. The important thing, as Volta discovered when he experimented with all sorts of different materials, was "the difference in the metals." What was really happening was that the two different metals, connected through the moist, fleshy, froggy tissue, were producing electricity chemically.

Volta managed to recreate this effect with discs of two different metals, silver and zinc, separated by pieces of cardboard soaked in saltwater, and that was how he came to invent the world's first proper battery—an invention that revolutionized the history of electricity. It was a perfect example of how a scientific discovery can be rapidly turned into a practical technology—and one that allowed science to advance even further by making experiments easier. Even in Volta's time, the discovery was considered so impressive that the inventor was asked to demonstrate it before the great French emperor Napoleon I, who set up the Galvanism Prize in his honor. (His nephew, Napoleon III, set up a Volta Prize to reward great scientific discoveries some years later.)

Volta's invention also led to the development of a new branch of science called electrochemistry. One of its founding fathers, Sir Humphry Davy (1778–1829), used a kind of electrochemistry known as electrolysis (effectively, making a battery work in reverse) to discover a number of chemical elements, including sodium and potassium, and later barium, calcium, magnesium, and strontium. Fittingly, he was awarded a Galvanism Prize for his work in 1807.

Magnetic attractions

There's electricity—and there's magnetism. That's how people like William Gilbert saw the world and it's still how we study it in schools to this day. The idea is not wrong, but it's a little bit misleading, because electricity and magnetism are essentially two different ways of looking at the same, bigger phenomenon. They're like two sides of the same coin or the front and back of a house. There had been various clues about the links between electricity and magnetism over the years. (In 1735, for example, the scientific journal Philosophical Transactions of the Royal Society of London had carried "An account of an extraordinary effect of lightning in communicating magnetism": according to a doctor in Yorkshire, a lightning bolt had struck the corner of a house where a large box of metal knives and forks were stored, scattering them around and, curiously, magnetizing them in the process.) But the definitive connection between electricity and magnetism was really first established by a series of revolutionary experiments that European scientists carried out in the 19th century.

The person who gets the credit for discovering what we now know as electromagnetism was Danishman Hans Christian Oersted (1777–1851), a physics professor in Copenhagen who had been inspired by Volta's invention of the battery. [6] Around 1820, during a student lecture, he just happened to place a compass near an electric wire and switched on the current. Incredibly, he noticed that the sudden current made the compass needle move, while reversing the current made the needle move the opposite way, suggesting the electricity flowing through the wire was making magnetism (because that's what a compass detects). [7] Though this was a major discovery, it wasn't the first proof of electromagnetism. About 20 years earlier, an Italian philosopher named Gian Domenico Romagnosi (1761–1835) had done a similar experiment, but few remember him today. [8]

Animation: Oersted's experiment: When he placed a compass near a wire and switched on the current, the compass needle moved one way; when he reversed the current in the wire, the needle moved the opposite way.

After learning of Oersted's work, Frenchman Andre-Marie Ampère (1775–1836) carried out another groundbreaking experiment with two wires placed side by side. When he switched on the current, he found the wires could push apart or pull together. One of his important conclusions was that a current-carrying wire makes a magnetic field at right angles, in concentric circles around the wire—rather like the ripples on a pond when you drop a stone into it.

This was all very interesting, but what use could it possibly be? Step forward English chemist and physicist Michael Faraday (1791–1867), originally an assistant to Sir Humphry Davy, who took "Ampère's beautiful theory" (as he called it) a stage further. [10] Ingeniously, he found he could make a wire rotate by passing electricity through it, because the flowing current created a magnetic field around it that would push against the field of a nearby magnet—and so invented a very primitive and not very practical electric motor. A few years later, he realized this invention would also work in reverse: if he moved a wire through a magnetic field, he could make electricity surge through it. That marked the invention of the electricity generator—a simple but revolutionary device that now provides virtually all the electricity we use to this day. Faraday, though he stood on the shoulders of Oersted, Ampère, and those who came before, arguably made the greatest contribution to our modern age of electric power.

Photo: Joseph Henry, America's answer to Michael Faraday, is honored by this statue at the US Library of Congress Thomas Jefferson Building. Photo by Carol M. Highsmith. Credit: Library of Congress Series in the Carol M. Highsmith Archive, courtesy of Library of Congress, Prints and Photographs Division.

Faraday wasn't the only pioneer of electromagnetism, however. Elsewhere in the UK, William Sturgeon (1783–1850), a brilliant but undeservedly forgotten inventor, was carrying out very similar experiments. In 1825, between Faraday's inventions of the electric motor and generator, Sturgeon built the first powerful electromagnet by coiling wire around an iron bar and sending a current through it. Over in the United States, in 1831, physicist Joseph Henry (1797–1879) made far bigger and better electromagnets (reputedly boosting the strength of the magnetic field by using wire insulated with cloth torn from his wife's undergarments) until he'd built a huge electromagnet that could lift a ton in weight. [11] Powerful electromagnets like this are still used in junkyards to this day to heave metal car bodies from one place to another. The following year, Sturgeon built the first practical, modern electric motor, using an ingenious device called a commutator that keeps the motor's axle rotating in the same direction.

A powerful force

Motors and generators—two parts of Faraday's very impressive legacy—are the twin bedrocks of our modern electric world. Generators make electric power, motors take that power and do useful things, from pushing electric cars down the road to sucking up dirt in your vacuum. But electrical energy doesn't come from thin air; as Volta showed, it doesn't even come magically from dead animals. If we want a certain amount of electrical energy, we have to produce it from at least as much of another kind of energy. That's a basic law of physics known as the law of conservation of energy, largely figured out by Scottish physicist James Prescott Joule (1818–1889) in the 1830s. Joule showed how different kinds of energy—including ordinary movement (mechanical energy), heat, and electricity—could be converted into one another. [13] What Joule's work means, essentially, is that if you want to run a huge city like New York or Sao Paulo off electricity, you'll need to harness huge amounts of some other kind of energy to do it. So, for example, you'll need a giant power station burning huge amounts of coal, hundreds of wind turbines, or a vast area of solar cells.

Photo: Power pioneer: Thomas Edison built the first practical power plants, which made electricity from coal using dynamos like this evolved by Michael Faraday's generator. Photo by H.C. White Co., courtesy of US Library of Congress.

Making enough energy to supply towns and cities with electricity became possible when a Belgian engineer named Zénobe Gramme (1826–1901) built the first large-scale, practical direct-current (DC) generators in the 1870s. In 1881, the world's first power plant opened in the small town of Godalming, England. The following year, Thomas Edison (1846–1931) built the first full-scale power plant at 257 Pearl Street in Manhattan, New York City. While Edison opted for plants that produced DC electricity, his former employee turned bitter rival Nikola Tesla (1856–1943) thought alternating current would work much better, since, among other things, it could be used to transmit power efficiently over very long distances. Tesla teamed up with engineer George Westinghouse (1846–1914), and the two launched a bitter battle with Edison—now known as the War of the Currents—until they'd firmly established AC as the victor. Today, though AC remains the heart of the electricity "grid" systems that provide much of the world's power, DC has again grown in importance thanks, in particular, to things like solar cells, which generate direct (rather than alternating) current. [14]

Waving hello

Photo: James Clerk Maxwell. Public domain photo by courtesy of Wikimedia Commons.

By the end of the 19th century, electricity and magnetism were happily married in motors and generators, but what was the real connection between them? Why did one produce the other?

The mystery was largely solved in the second half of the 19th century by a brilliant Scottish physicist named James Clerk Maxwell (1831–1879). In 1873, building on Michael Faraday's work, Maxwell published a complete theory of electromagnetism, neatly summarizing everything that was then known about electricity and magnetism in four apparently simple mathematical equations. Maxwell's theory explained how static or moving electric charges create electric fields around them, while magnetic poles (the ends of magnets) make magnetic fields. It also showed how electric fields can create magnetism and magnetic fields can make electricity, and tied electromagnetism together with light. This was one of the most fundamental and far-reaching theories of physics advanced so far—as radically important as Newton's work on gravity.

Of course, electricity and magnetism were just the same as they had always been. What was different, following the work of James Clerk Maxwell, was a bold new understanding of how they worked together: a revolutionary new piece of science. And as the 19th century rolled on, technology advanced too: with the work of Edison, Tesla, and others, there was a growing understanding of how electromagnetism could put to good use as a practical way of storing and transmitting energy. All that was remarkable enough, but thanks to Maxwell's insights, linking electricity and magnetism to light waves, electromagnetism would soon change the world in another very important way: as a form of communication.

Photo: Champion of radio: Guglielmo Marconi didn't discover the basic science behind radio, but his amazing demonstrations of its usefulness transformed it into a winning technology. Color lithograph charicature of Marconi by Sir L. Ward (Spy), 1905. courtesy of the Wellcome Collection published under a Creative Commons Attribution 4.0 International (CC BY 4.0) licence.

The first inkling of an exciting new form of electromagnetism came the decade after Maxwell had died. Maxwell had realized that electromagnetism could travel in waves. In 1888, a German physicist named Heinrich Hertz (1857–1894) found he could make some of these waves, in which electrical and magnetic energy tangoed through the air at the speed of light. [15] Apart from confirming Maxwell's ideas, this scientific advance opened up another new bit of technology: a practical way for sending information wirelessly from one place to another. English physicist Sir Oliver Lodge (1851–1940), who had been carrying out similar research to Hertz, and Italian Guglielmo Marconi (1874–1937), a brilliant showman with a gift for popularizing science, were among those who developed this technology. Originally called "ether waves," and now much better known to us as radio, it evolved into radar, television, satellite communication, remote control, Wi-Fi, and a whole variety of other things.

The source of electricity

Electricity has always been magical. Imagine how enthralled Thales must have been when he first saw static over 2500 years ago. Or what Heinrich Hertz felt like as he made the first radio waves in his laboratory in Karlsruhe in 1888. At the dawn of the 20th century, electricity seemed magical in all sorts of ways. Thomas Edison was building bold power plants and switching the world to the wonders of incandescent electric light. Marconi, meanwhile, was bouncing radio waves around the world. And there was a new kind of electrical magic as well: the dawning realization that electricity and magnetism originated from tiny particles inside atoms.

The idea that there must be a kind of "particle of electricity" had originally been put forward in 1874 by Irishman George Johnstone Stoney (1826–1911), who had previously studied the kinetic theory (how gas particles carried heat). [16] Similar ideas were advanced in 1881 by German physicist Hermann von Helmholtz (1821–1894) and Dutchman named Hendrik Antoon Lorentz (1853–1928); together, these three developed the modern "particle" theory of electricity, in which static charges are seen as a build up of electric particles, while electric currents involve a flow of these particles from place to place. But what were the particles? The growing understanding of atoms and the world inside them, by Ernest Rutherford (1871–1937) and his colleagues, offered up a possible candidate in the shape of the electron, a particle Stoney named in 1891. Electrons were finally discovered in 1897 by British physicist J.J. Thomson (1856–1940), while he was playing around with a gadget called a cathode-ray tube, rather like an old-fashioned TV set. [17]

Animation: Solid-state physics explains that electric current is carried by electrons (blue) moving through materials.

During the 20th century, scientists came to understand not just how electrons power electricity and magnetism, but how they're involved in all kinds of other physical phenomena, including heat and light. Known as solid-state physics, these scientific ideas have led to some revolutionary electronic technologies, including the transistor, integrated circuits for computers, solar cells, and superconductors (materials with little or no electrical resistance).

Today, as the world grapples with pressing problems like air pollution and climate change, the need to switch from dirty fuels to cleaner forms of power has made electricity more important to us than ever. Back in Thales' time, electricity was just a take-it-or-leave-it, magical curiosity; today, it's central to our world and everything we do. The story of electricity runs, like a current, right through our past. Thanks to the brilliant work of these scientists and inventors, it also points to a bright and hopeful future.

Find out more

On this website

• Batteries
• Electric motors
• Electronics
• Magnetism
• Power plants
• Static electricity

Books

For younger readers

• The Attractive Story of Magnetism with Max Axiom, Super Scientist by Andrea Gianopoulos. Capstone Press, 2008/2019. A graphic book with a companion app.
• Scientific Pathways: Electricity by Chris Woodford. Rosen, 2013: My quick introduction to electrical history. Previously published by Blackbirch in 2004 under the series title Routes of Science.
• Charged Up: The Story of Electricity by Jackie Bailey and Matthew Lilly. Picture Window Books/A & C Black, 2004. A graphic-style history that will appeal to reluctant readers.
• DK Biographies: Thomas Edison by Jan Adkins. DK, 2009. A well-illustrated, curriculum linked, short biography for younger readers aged 9–12.

For older readers

• The Age of Edison: Electric Light and the Invention of Modern America by Ernest Freeberg. Penguin, 2013.
• The Wizard of Menlo Park: How Thomas Alva Edison Invented the Modern World by Randall E. Stross. Crown Publishing Group, 2008.

Scholarly articles

• Bibliographical History Of Electricity And Magnetism by Paul Fleury Mottelay. Charles Griffin, 1922.
• Origin of the Electrical Fluid Theories by Fernando Sanford, The Scientific Monthly, Vol 13, No 5, Nov 1921, pp.448–459.
• Nikola Tesla by Kenneth M. Swezey, Science, Vol 127, No 3307, May 1958, pp.1147–1159.
• George Johnstone Stoney, F. R. S. and the concept of the electron by J.G. O'Hara, R.V. Jones, and W.D.P. Macdonald, Notes Rec. R. Soc. Lond, 1 March 1975.

Primary sources

If you want to read some of the original thoughts of pioneering electric scientists, try these:

• Great Experiments in Physics: Firsthand Accounts from Galileo to Einstein by Morris H. Shamos. Dover, 1959/1987. A wonderful collection of original papers, including groundbreaking electromagnetic experiments by Hans Christian Oersted, Michael Faraday, James Joule, J.J. Thomson, and Robert Millikan.
• Experiments and Observations, Tending to Illustrate the Nature and Properties of Electricity by William Watson, Philosophical Transactions, 1753.
• De Magnete: Book 2, Chapter 2: On the Attraction of Amber, or more truly, on the Attaching of Bodies to Amber by William Gilbert, in Gilbert of Colchester: Father of Electrical Science by Silvanus P. Thompson, Chiswick Press, 1903.
• Experiments and Observations on Electricity by Benjamin Franklin, The American Journal of Science and Arts, 1769.
• On the Production of Currents and Sparks of Electricity from Magnetism by Joseph Henry, The American Journal of Science and Arts, 1832.

References

1. ↑   Bibliographical History Of Electricity And Magnetism by Paul Fleury Mottelay. Charles Griffin, 1922, p.1.
2. ↑   Ancient Egyptian Antimony Plating on Copper Objects: A Rediscovered Ancient Egyptian Craft by Colin G. Fink and Arthur H. Kopp, Metropolitan Museum Studies, Vol 4, No 2, March 1933, pp.163–167.
3. ↑   Magic in Ancient Greece by Mark Cartwright, Ancient History Encyclopedia, 2016.
4. ↑   Thales of Miletus by Patricia O'Grady, Internet Encyclopedia of Philosophy.
5. ↑   Origin of the Electrical Fluid Theories by Fernando Sanford, The Scientific Monthly, Vol 13, No 5, Nov 1921, pp.448–459.
6. ↑   Speculation and Experiment in the Background of Oersted's Discovery of Electromagnetism by Robert C. Stauffer, Isis, Vol 48 No 1, March 1957, pp.33–50.
7. ↑   "Chapter 9: Hans Christian Oersted: Electromagnetism" in Great Experiments in Physics: Firsthand Accounts from Galileo to Einstein by Morris H. Shamos. Dover, 1959/1987, p.121.
8. ↑   It remains a matter of debate whether Oersted knew of, or was influenced by, Romagnosi's experiment. See for example Bibliographical History Of Electricity And Magnetism by Paul Fleury Mottelay. Charles Griffin, 1922, p.365; Speculation and Experiment in the Background of Oersted's Discovery of Electromagnetism by Robert C. Stauffer, Isis, Vol 48 No 1, March 1957, pp.33–50.
9. ↑   Speculation and Experiment in the Background of Oersted's Discovery of Electromagnetism by Robert C. Stauffer, Isis, Vol 48 No 1, March 1957, p.33.
10. ↑   "Beautiful theory": "Chapter 10: Michael Faraday: Electromagnetic Induction and Laws of Electrolysis" in Great Experiments in Physics: Firsthand Accounts from Galileo to Einstein by Morris H. Shamos. Dover, 1959/1987, p.131.
11. ↑    Henry discusses this in On the Production of Currents and Sparks of Electricity from Magnetism by Joseph Henry, The American Journal of Science and Arts, 1832.
12. ↑   Franklin describes the kite experiment in "Letter XI," Experiments and Observations on Electricity by Benjamin Franklin, The American Journal of Science and Arts, 1769, p.111.
13. ↑   "Chapter 12: James Joule: The Mechanical Equivalent of Heat" in Great Experiments in Physics: Firsthand Accounts from Galileo to Einstein by Morris H. Shamos. Dover, 1959/1987, p.166.
14. ↑   Some reasons for DC's resurgence are set out in Edison's Final Revenge: The system of DC power generation and local distribution that the great inventor championed is set for a comeback by David Schneider, American Scientist, Vol 96 No 2, March–April 2008, pp.107–108.
15. ↑   "Chapter 13: Heinrich Hertz: Electromagnetic waves" in Great Experiments in Physics: Firsthand Accounts from Galileo to Einstein by Morris H. Shamos. Dover, 1959/1987, p.184.
16. ↑   "George Johnstone Stoney, F.R.S., and the Concept of the Electron by J. G. O'Hara, Notes and Records of the Royal Society of London, Vol 29, No 2, March 1975, pp.265–276.
17. ↑   "Chapter 16: J.J. Thomson: The Electron" in Great Experiments in Physics: Firsthand Accounts from Galileo to Einstein by Morris H. Shamos. Dover, 1959/1987, p.216.