The history
From a twitching compass needle to the generators that make almost all the world's electricity.
In 1820 people learned that a current makes magnetism. For eleven years scientists tried to make it work the other way round, and failed, because they were waiting for a steady effect. Michael Faraday found that a magnet only makes a current while something is changing. That one idea gave us the generator, the transformer, the induction motor, radio waves, and the wireless charger on your desk.
1820
Electric current shown to make magnetism
Hans Christian Ørsted, Denmark
1821
Electricity turned into continuous motion
Michael Faraday, England
1831
Electromagnetic induction discovered and published
Michael Faraday, England
1831
First electric generator (the Faraday disc)
Michael Faraday, England
1832
First dynamo with a commutator
Hippolyte Pixii, France
1866–1867
Self-excited dynamo
Varley, Siemens and Wheatstone, England and Germany
1882
Hydroelectric central station for customers in North America
Vulcan Street Plant, Appleton, USA
1884–1885
Efficient closed-core transformer
Zipernowsky, Bláthy and Déri, Hungary
1897
India's first hydroelectric power station
Sidrapong, Darjeeling, India
2010
Qi wireless charging standard, version 1.0
Wireless Power Consortium
1820 – 1830
A current is found to move a magnet. Scientists hunt for the reverse, and spot strange effects they cannot explain.
1820
Spring 1820, published 21 July 1820
Ørsted showed that a wire carrying current swings a nearby compass needle. He described it in a short Latin pamphlet dated 21 July 1820 and posted it to scientists all over Europe.
Why it mattered. Electricity could make magnetism. Everyone now asked: can magnetism make electricity?
1821
September 1821
Faraday made a wire carrying current spin round and round a magnet standing in a cup of mercury. It was the first time electricity had been turned into steady motion.
Why it mattered. It is the ancestor of every electric motor, and it set Faraday thinking about forces curling around wires.
1824
22 November 1824
Arago found that a spinning copper disc drags a magnetic needle hung above it, even though copper is not magnetic. Nobody could explain why.
Why it mattered. It was induction hiding in plain sight. Faraday explained it in 1831: the moving disc has swirling 'eddy' currents inside it.
1831 – 1834
Faraday discovers induction and builds the first generator. Henry finds it too, Pixii builds a dynamo, and Lenz explains which way the current flows.
1831
29 August 1831
Faraday wound two coils of wire on opposite sides of an iron ring. When he connected a battery to one coil, a meter on the other coil flicked, then fell back to zero. It flicked again, the other way, when he disconnected it.
Why it mattered. A current appears only while the magnetism is changing. That is Faraday's law, and the ring was the first transformer.
1831
October 1831
Faraday pushed a bar magnet in and out of a coil and the meter jumped every time it moved. On 28 October he spun a copper disc between the poles of a big magnet and got a steady current from it. He read his results to the Royal Society on 24 November 1831.
Why it mattered. The Faraday disc was the first electric generator: motion in, electricity out.
1832
c. 1830–1832
Henry, a teacher at the Albany Academy, built some of the strongest electromagnets in the world. He saw induction on his own, and also self-induction, where a coil pushes back against changes in its own current. Faraday published first, so Faraday got the credit.
Why it mattered. The unit of inductance, the henry, was named after him in 1893.
1832
Pixii, an instrument maker, spun a horseshoe magnet past two coils with a hand crank. It made a current that flipped back and forth, so a switch called a commutator was added to make it flow one way.
Why it mattered. It was the first dynamo, the kind of machine that would later light cities.
1834
Lenz worked out which way an induced current flows: always so that its own magnetism fights the change that made it. Push a magnet towards a coil and the coil pushes back.
Why it mattered. Lenz's law is the minus sign in Faraday's law, and the reason a generator gets harder to turn when it powers something.
1861 – 1888
Maxwell turns Faraday's lines of force into equations and predicts that light is an electromagnetic wave. Hertz proves it.
1865
1861–1865
Maxwell turned Faraday's pictures of 'lines of force' into mathematics. His great paper, read to the Royal Society on 8 December 1864 and published in 1865, predicted waves of electricity and magnetism that travel at the speed of light.
Why it mattered. Faraday's law became one of Maxwell's equations, and light turned out to be electricity and magnetism inducing each other.
1887
1886–1888
Hertz noticed that a spark in one coil made a tiny spark jump in another nearby. He went on to show these were Maxwell's waves, travelling through the air and behaving like light. He published from November 1887.
Why it mattered. Maxwell was right, and radio, TV and Wi-Fi all follow from it.
1866 – 1902
Dynamos, transformers and induction motors turn a lab trick into power stations, from Wisconsin to Budapest to Karnataka.
1867
December 1866 – early 1867
Early generators used weak permanent magnets. Varley, Siemens and Wheatstone each found, within weeks of each other, that a dynamo can feed part of its own current into electromagnets and make its field stronger and stronger. Ányos Jedlik in Hungary had the same idea around 1856.
Why it mattered. Big, cheap generators became possible, and the age of electric power began.
1882
30 September 1882
The Vulcan Street Plant used the Fox River to spin an Edison dynamo of about 12.5 kilowatts. It lit a house and two paper mills.
Why it mattered. It is recognised as North America's first hydroelectric central station serving private and commercial customers.
1885
1884–1885
Three engineers at the Ganz factory wound coils on a closed iron core, just like Faraday's ring, and got efficient transformers. They were shown at the Budapest National Exhibition in 1885.
Why it mattered. Transformers let power travel far at high voltage and arrive safely at low voltage, which is why homes use AC.
1886
20 March 1886
Stanley, working for George Westinghouse, sent alternating current along the main street at high voltage and used transformers to step it down for the shops and offices.
Why it mattered. It was the first complete system of generator, transformers and high-voltage AC line.
1888
1885–1888
Ferraris in Turin and Tesla in New York each made a magnetic field that rotates. It induces currents in a metal rotor, which chases the field round with no sliding contacts. Ferraris published in April 1888 and Tesla's patents were granted in May 1888.
Why it mattered. Induction motors now spin most fans, pumps, washing machines and factory machines.
1897
10 November 1897
A small plant in the hills below Darjeeling began making electricity from mountain streams, with two 65 kW generators. It sold power to the public.
Why it mattered. It is recognised as India's oldest hydroelectric power station.
1902
30 June 1902
Generators at the Shivanasamudra falls sent power 147 km to the Kolar Gold Fields, said to be the longest power line in the world at the time. From 1905 it also lit Bangalore.
Why it mattered. It is often called Asia's first large hydroelectric transmission scheme. Japan's smaller Keage plant in Kyoto had started in 1891.
By the numbers
World electricity generation grew about 5,000 times in 125 years. Apart from solar panels, almost all of it comes from spinning generators that work by Faraday's law.
1931 – today
Induction moves into guitars, kitchens and phones, with no wires touching at all.
1932
1931–1932
Beauchamp's 'Frying Pan' guitar had magnets and a coil around its steel strings. As a string vibrates it changes the magnetism through the coil and induces a tiny current that an amplifier makes loud. Prototype 1931, sold from 1932.
Why it mattered. Every electric guitar pickup is a tiny Faraday generator.
1971
Westinghouse showed its 'Cool Top' induction range. A coil under the glass makes a fast-changing field, which induces currents in the iron pan itself. The pan gets hot and the glass stays fairly cool.
Why it mattered. Heat appears right inside the pan, so induction hobs waste less energy than flames.
2010
2008–2010
Companies formed the Wireless Power Consortium in December 2008 and released version 1.0 of its Qi standard in 2010. A coil in the pad and a coil in the phone work like the two halves of Faraday's ring. Qi2, with magnets to line the coils up, followed in 2023.
Why it mattered. Faraday's 1831 ring now sits in millions of phones and chargers.
Did you know?
A magnetic flux changing by one weber every second induces exactly one volt.
Four units honour this story: the farad (named 1881), the henry (1893), the weber (recommended 1935) and the tesla (1960).
In 2025 solar panels made about 9% of the world's electricity. Nearly all the rest came from generators turning coils and magnets past each other, just as Faraday did.
Faraday's 1831 ring and generator are still on display at the Royal Institution in London.
The famous story that Ørsted discovered electromagnetism by accident in the middle of a lecture is probably a myth: he had been looking for it since 1818.
In the 1950s Frigidaire showed an induction stove heating a pot of water with a sheet of newspaper between the hob and the pot.
Faraday's law has a minus sign in it: ℰ = −dΦ/dt. That minus sign is Lenz's law, the induced current fighting the change.
An electric guitar pickup, a wireless charger and a power-station generator all run on the same 1831 discovery.
The people
1791 – 1867 · Chemist and physicist · England
A blacksmith's son with little schooling who discovered induction and built the first generator.
1777 – 1851 · Physicist and chemist · Denmark
Showed that an electric current moves a compass needle, starting the whole hunt.
1797 – 1878 · Physicist and teacher · United States
Found induction and self-induction on his own; the henry is named after him.
1804 – 1865 · Physicist · Russian Empire (born in Dorpat, now Tartu, Estonia)
Worked out that an induced current always opposes the change that made it.
1831 – 1879 · Physicist · Scotland
Put Faraday's law into his equations and showed that light is an electromagnetic wave.
1860 – 1939 · Engineer · Hungary
Co-invented the practical closed-core transformer at the Ganz Works in Budapest.
1856 – 1943 · Engineer and inventor · Austrian Empire (now Croatia); worked in the United States
Patented the AC induction motor; the tesla, the unit of magnetic field, is named after him.
1845 – 1901 · Dewan (chief minister) of Mysore · India
Started the Shivanasamudra hydro scheme, but died the year before it first sent power.
Where it happened
Sources
Dates marked “c.” are approximate, and historians sometimes disagree about who was first. If you spot a mistake, tell us.
↑↓ move↵ open/ or ⌘K search anywhere