On our power poles and in our power supplies, in our communication equipment and in our cars, transformers help distribute power, isolate signals, and create voltage to spark our ignition. Transformers, sending electrical energy from one coil of wire to another, convert varying electrical current into changing magnetism, and then back to electrical current.
Like most inventions though, transformers did not suddenly appear on the scene. Over many years a series of discoveries and inventions, when linked together, evolved into the transformers we have today.
Some 2800 years ago, one of the first discoveries was made independently by the Greeks and the Chinese. They noticed that lodestones would attract. Because of this attraction, the Greeks named them magnets.
Advancements toward transformers, beyond the lodestone, did not occur until the late 1500's with William Gilbert, a mathematician. He was one of the first to use scientific methods to investigate the phenomenon of magnetism. In 1600, likening the polarity of a magnet to the polarity of the earth, he published his findings on magnetism.
Between 1785 and 1791, Charles Coulomb who was also a mathematician published papers showing the inverse square laws of repulsion, both for electrical force and magnetic force.
Magnetism and Electricity
Hans Christian Oersted, in 1820, discovered that passing an electrical current through a coil of wire produced magnetism. That discovery, that electricity causes magnetism, was an important step in the invention of the transformer.
In 1831, more of the ideas required for the transformer were understood. The discovery of electro-magnetic induction was made independently by Michael Faraday and Joseph Henry. They had found out that a changing a magnetic field, inside a coil of wire, induced an electrical current in the coil.
Then in 1836, while giving a demonstration to a class he was teaching, Nicholas Joseph Callan (professor of Natural Philosophy, now called Physics) placed two coils of wire next to each other. Having first connected a battery to one of the coils, he disconnected the battery; a spark jumped between the wires on the second coil. Using magnetism, electrical power had been induced in a second coil of wire using electrical current in the first. This was a transformer. Power had been transferred from one coil of wire to another using an electrically induced magnetic field.
Between the 1830s and the 1870s, experiments, mostly using trial and error, revealed the basic principles of transformers.
By 1876 the Russian engineer Pavel Yablochkov was using coils, essentially transformers, for an arc lighting system. By 1885, Ottó Bláthy, Miksa Déri and Károly Zipernowsky, from the Ganz factory in Budapest, started manufacturing transformers to distribute power for electric lighting. They had over fifty power systems installed in Austria-Hungary.
Transformers, since their original use for power distribution, are also employed in many other applications. They're used in audio, video, RF, and instrumentation. They increase or decrease voltage; they increase or decrease current. Transformers can be as small as a few millimeters across or as large as a school bus.
Today the basic principles of the transformer, with all the variations, are still the same. A transformer changes electrical energy from a varying current in one coil of wire into a fluctuating magnetic field. This magnetic field then passes its energy to another coil in the form of varying electrical current.