An electromagnet is a type of Magnet in which the magnetic field is produced by an electric current. In its simplest form, it consists of a wire wound into a coil. When an electric current flows through the wire, it generates a magnetic field. This field is concentrated in the hole in the center of the coil, known as the bore. The magnetic field disappears when the current is turned off. For practical applications, the coil of wire is often wrapped around a core of ferromagnetic material, such as soft iron. This core material becomes strongly magnetized by the field from the coil, and its own magnetic field adds to the coil's, creating a far more powerful magnet. The electromagnet is a temporary magnet; its defining characteristic is that its magnetic force can be quickly changed by controlling the amount of electric current in the winding. It is this unique property of controllable magnetism that has made the electromagnet one of the most fundamental and versatile components of modern technology, an invisible hand that powers, moves, communicates, and reveals the world around us.
Long before the electromagnet could be conceived, its two parent forces, electricity and magnetism, lived entirely separate lives in the human imagination. They were parallel mysteries, twin wonders of the natural world, each with its own mythology, its own portfolio of strange behaviors, yet with no known kinship. Magnetism was the more ancient and tangible of the two. Its story begins with the discovery of the Lodestone, a naturally magnetized piece of the mineral magnetite. Shepherds and miners in the ancient world, perhaps in the region of Magnesia in Anatolia (from which “magnetism” likely derives its name), would have noticed these strange, dark stones that could cling to iron tools or attract each other with an unseen force. Plato and Pliny the Elder wrote of this “living stone,” attributing its power to divine or spiritual properties. For centuries, it was a curiosity, a tool for magicians and a subject of philosophical debate. Its first truly world-changing application came with the invention of the Compass. By suspending a sliver of lodestone or a magnetized iron needle so it could pivot freely, ancient mariners, likely in Song Dynasty China around the 11th century, discovered it would unfailingly align itself with the Earth's own immense magnetic field. This simple device unlocked the oceans, transforming navigation from a coastal, landmark-dependent art into a global science, enabling the Age of Discovery and the weaving together of distant continents. Yet, the force itself remained a profound enigma. Electricity, meanwhile, had a far more ethereal and fleeting presence. Its discovery is credited to the ancient Greeks, around 600 BCE, when Thales of Miletus observed that amber (elektron in Greek, the root of “electricity”) rubbed with fur or wool would attract light objects like feathers or straw. This phenomenon, now known as static electricity, was seen as a unique property of amber. For over two millennia, it progressed little beyond this parlor trick. It was a phantom force, one that could be coaxed into existence for a moment, only to vanish without a trace. It lacked the persistent, physical presence of the lodestone. The first great leap in untangling these forces came in 1600 with the English physician and scientist William Gilbert. In his masterwork De Magnete (“On the Magnet”), Gilbert conducted the first truly systematic, experimental study of both magnetism and static electricity. He meticulously cataloged the properties of the lodestone and demonstrated that the Earth itself was a giant magnet, thus providing the first scientific explanation for the behavior of the compass. He also distinguished clearly between the magnetic attraction of the lodestone and the static electric attraction of amber, noting that the latter could be induced in many other substances, like glass and sulfur. Despite his brilliant work, Gilbert concluded, like all who came before him, that the two forces were distinct and unrelated phenomena. And so, for another two centuries, electricity and magnetism continued their separate journeys—one steering ships across the world's oceans, the other a fleeting curiosity confined to the scientist's laboratory. The world was not yet ready for their union.
The moment of conception for the electromagnet—the instant when the two separate forces were finally revealed to be two sides of the same coin—arrived not with a thunderclap, but with the subtle twitch of a needle. The setting was a lecture hall at the University of Copenhagen in the spring of 1820. The man at the center of this quiet revolution was the Danish physicist and philosopher Hans Christian Ørsted. Ørsted was a man deeply influenced by the German philosophical movement of Naturphilosophie, which held that all of nature was a unified whole, and that a deep, underlying connection must exist between its various forces. He had long suspected a link between electricity and magnetism, but like many others, he had failed to find it. His previous experiments had been fruitless, often because he, like his contemporaries, assumed that if a connection existed, the magnetic force must radiate outwards from the wire in the same direction as the current flow, like light from a candle. The story of the discovery is a classic tale of scientific serendipity. During a private lecture for a group of advanced students, Ørsted was demonstrating the heating effects of an electric current passing through a platinum wire, powered by a new and powerful voltaic pile—an early form of Battery. On his demonstration table, by chance, lay a mariner's compass. As he connected the circuit, sending a powerful current through the wire, he noticed the compass needle jolt, abandoning its faithful alignment with the Earth's magnetic north and twisting to stand nearly perpendicular to the wire. It was a small motion, one that a less prepared mind might have dismissed as an accidental bump or vibration. But for Ørsted, it was everything. He had been looking for a connection for years, and here it was, an undeniable interaction. The electric current was creating a magnetic field. After the lecture, he experimented further, confirming the effect. He discovered that the force was not radiating straight out from the wire, but was instead acting in a circle around it. This was a bizarre, non-intuitive concept. No other known force in physics behaved this way. In July 1820, Ørsted published his findings in a short, four-page pamphlet in Latin, which he circulated to scientific societies across Europe. The news spread like wildfire. The intellectual dam that had separated the two fields for millennia had been breached. Scientists everywhere, from André-Marie Ampère in France to Michael Faraday in England, immediately dropped their work to replicate and expand upon Ørsted's discovery. Ampère quickly formulated the mathematical law describing the magnetic force between two electric currents, laying the foundations for the field of electrodynamics. The world had been irrevocably altered. A new force of nature had been unveiled—electromagnetism—and the stage was set for the birth of a device that would harness it.
Ørsted's discovery was a profound scientific revelation, but the circular magnetic field around a single, straight wire was weak and diffuse. It could deflect a delicate compass needle, but it couldn't perform any real work. The challenge was to concentrate this newfound force, to bundle it into a tool with tangible power. This next crucial step from scientific principle to practical device—the actual birth of the electromagnet—was taken by an unlikely and resourceful Englishman named William Sturgeon. Sturgeon was not a university-educated academic but a former soldier and self-taught shoemaker with a passion for science. Lacking the formal training of his contemporaries, he possessed a brilliant, intuitive knack for invention. In 1825, just five years after Ørsted's discovery, Sturgeon conceived of a way to amplify the magnetic effect. He took a seven-ounce piece of iron, bent it into the shape of a horseshoe, and gave it a coat of insulating varnish. Then, he loosely wrapped a single layer of bare copper wire around it, with about 18 turns in total. His logic was simple but revolutionary. He reasoned that by coiling the wire, he could make the magnetic field from each turn add up, concentrating the force within the coil. Furthermore, by placing an iron core inside the coil, he hoped the iron itself would become magnetized, adding its own strength to the mix. The result was a resounding success. When Sturgeon connected the ends of his wire to a single-cell battery, his modest device became a powerful magnet. It was able to lift a nine-pound lump of iron—more than twenty times its own weight. When the battery was disconnected, the iron core instantly lost its magnetism, and the nine-pound weight clattered to the floor. Sturgeon had created the world's first controllable, powerful magnet. He had built the first electromagnet. He presented his invention to the Society of Arts in London in 1825, winning a silver medal. Sturgeon's electromagnet was a marvel. It was not just stronger than any permanent magnet of a similar size; it was dynamic. Its power could be switched on and off at will. This was its true genius. For the first time, humans could command a powerful magnetic force with the simple flick of a switch. While Sturgeon's creation was still a scientific curiosity, it was a functional one. It proved that the invisible force of electromagnetism could be tamed, shaped, and put to work. It was the embryonic form of a technology that would soon grow to lift cars, carry voices across continents, and power the modern world.
While William Sturgeon had given birth to the electromagnet, it was an American physicist, Joseph Henry, who would nurture it from a clever infant into a veritable giant. Working in relative isolation at the Albany Academy in New York during the late 1820s and early 1830s, Henry transformed Sturgeon's nine-pound-lifting novelty into a force of astonishing power, laying the practical groundwork for much of the technology that would follow. Henry's key insight was deceptively simple but technically brilliant. Sturgeon's design used a loose, single layer of uninsulated wire wrapped around a varnished core. This limited the number of turns that could be used, as the turns could not touch each other without short-circuiting. Henry realized that the key to a more powerful magnet was to pack as many turns of wire as possible into the smallest space. To do this, he needed to insulate the wire, not the core. Using silk thread from his wife's petticoats, he painstakingly wrapped thin copper wire, insulating it along its entire length. This innovation allowed him to wind the wire in tight, successive layers around the iron core, one on top of the other, without fear of short circuits. Each additional turn of wire contributed its magnetic field, and the effect was cumulative. The results were staggering.
In 1831, Henry constructed what became known as the “Great Magnet of Yale.” Built for Professor Benjamin Silliman at Yale University, this electromagnet was a testament to his new design principles. It weighed a mere 21 pounds, but with the current from a small battery flowing through its meticulously wound coils, it could hoist an incredible 2,063 pounds of iron—nearly one ton. Demonstrations of this magnet became legendary academic spectacles. Students and faculty would watch in awe as this small, inert object was brought to life, effortlessly lifting massive weights that would have required a team of strong men to budge. Henry had not just improved the electromagnet; he had created a new class of machine. He systematically studied the relationship between the battery, the coils, and the resulting magnetic strength, establishing two distinct types of electromagnets:
It was this second invention, the “intensity magnet,” that held the key to the future. In 1831, to demonstrate its potential, Henry strung over a mile of wire around a lecture room at the Albany Academy. At one end, he placed his intensity magnet. At the other, he had a small battery and a switch. When he closed the switch, the current traveled through the mile of wire and activated the electromagnet at the far end, causing it to attract a small permanent magnet, which in turn struck a bell. Clang. He had created the first audible electric signaling system. This device was, in essence, the world's first electric relay and the direct ancestor of the electric Telegraph. Henry had not only shown how to create immense magnetic power but also how to project that power over a vast distance. He had invented the fundamental component that would allow humanity to send messages at the speed of light.
For millennia, the speed of information had been bound by the speed of a horse, a train, or a ship. News of war, the prices of goods, personal tidings—all traveled at a frustratingly terrestrial pace. Joseph Henry's intensity magnet and signaling device, however, contained the blueprint for shattering this ancient limitation. The electromagnet was about to find its first world-changing purpose: to become the heart of a machine that would conquer distance and time. The story of the Telegraph is most famously associated with the artist-turned-inventor Samuel F. B. Morse. While visiting Europe in 1832, Morse was captivated by a demonstration of electromagnetism. He became obsessed with the idea of using it to send messages. He envisioned a system of dots and dashes—what would become Morse Code—that could be transmitted electrically. However, Morse, lacking a deep scientific background, struggled for years to make his device work over anything more than a short length of wire. The signal would fade, becoming too weak to activate his receiver. The solution to his problem lay in the work of Joseph Henry. In 1837, Morse was introduced to Henry's concept of the “intensity magnet” and, crucially, the relay. The relay was a stroke of genius. It was an electromagnet used not to do heavy lifting but to act as a remote-controlled switch. A weak, long-distance signal would flow into the relay's coil. This was just enough to create a small magnetic pull, which would close a switch on a separate, local circuit powered by its own fresh battery. This local circuit could then power another relay further down the line, or it could power the final “sounder”—an electromagnet that would click loudly, transcribing the dots and dashes for a waiting operator. With Henry's relay, the signal could be renewed and re-amplified at intervals, allowing messages to be sent across hundreds, and eventually thousands, of miles. The electromagnet was the core component at every critical stage:
On May 24, 1844, the system had its triumphant public debut. From the U.S. Supreme Court chamber in Washington, D.C., Morse tapped out the biblical phrase, “What hath God wrought!” The message traveled almost instantaneously along 40 miles of wire to Baltimore, where it was received and confirmed. The world shrank in that moment. The societal impact was explosive. Telegraph lines, strung on poles, began to trace the paths of railroads across the continent.
By 1866, a transatlantic cable connected North America and Europe. The electromagnet, clicking away in quiet offices on both sides of the ocean, had become the voice of a new, interconnected global civilization.
The telegraph was a revolution in information, but the electromagnet's next great act was to be a revolution in power. While the telegraph used tiny currents to transmit intelligence, a new generation of scientists and inventors realized that the principles of electromagnetism could be scaled up to generate and utilize massive amounts of energy. The invisible hand was about to become an invisible engine, reshaping cities, factories, and homes. The key to this transformation was a discovery made in 1831 by the English scientist Michael Faraday, a contemporary of Henry and one of the greatest experimental physicists in history. If Ørsted had shown that electricity could create magnetism, Faraday wondered if the reverse was true: could magnetism create electricity? Through a series of elegant experiments, he proved that it could. He found that moving a magnet near a coil of wire, or moving a coil of wire near a magnet, would induce an electric current in the wire. This principle is known as electromagnetic induction. This discovery revealed a beautiful and profound symmetry in nature. It also provided the theoretical basis for two of the most important machines ever invented: the electric Generator and the electric Motor.
A Generator (or dynamo) is essentially a device that uses electromagnetic induction to convert mechanical energy (like the turning of a crank or a water wheel) into electrical energy. In a practical generator, powerful electromagnets (called field coils) create a strong magnetic field. Within this field, another set of wire coils (the armature) is rotated by an external force, such as a steam engine or a water turbine. As the armature's wires cut through the magnetic field lines, a current is induced within them. The faster the rotation, the stronger the magnetic field, the more electricity is produced. In the 1870s, inventors like Zénobe Gramme in Belgium and Friedrich von Hefner-Alteneck in Germany developed the first efficient, large-scale direct current (DC) dynamos. These machines, with their powerful electromagnets, were capable of producing a steady, powerful flow of electricity. They became the workhorses of the new electrical age, most famously championed by Thomas Edison. His Pearl Street Station, opened in New York City in 1882, used massive steam-powered dynamos to power his incandescent light bulbs, illuminating a small section of Manhattan and heralding the dawn of electric light.
The electric Motor is the perfect mirror image of the generator. If you take a generator and, instead of turning it mechanically, you feed it electricity, it will begin to turn. The current flowing into the armature coils turns them into temporary electromagnets. These electromagnets are then repelled and attracted by the stationary field coils, creating a continuous rotational force, or torque. The electric motor offered a revolutionary new form of power. Unlike the hulking, centralized steam engine that relied on a complex and dangerous system of belts and pulleys to distribute power throughout a factory, the electric motor was compact, efficient, and could be placed exactly where it was needed. Frank J. Sprague's development of a practical DC motor in the 1880s led to the first electric elevators and electric streetcar (trolley) systems, which transformed urban landscapes and allowed cities to expand outward. In factories, electric motors allowed for more flexible and efficient assembly lines, dramatically boosting industrial productivity and fueling the Second Industrial