When was Faradays law discovered

Michael Faraday
Authors: Thomas Seilnacht and Peter Buck
born on September 22, 1791 in Newington near London
died on August 25, 1867 in the Royal Park of Hampton Court

curriculum vitae

Michael Faraday was born the third of four siblings in London. His father was a farrier; the family lived in very modest circumstances. The bookseller and bookbinder Ribeau recognized the reliability of his 13-year-old newspaper delivery boy Michael Faraday, so he offered him an apprenticeship as a bookbinder and - what was even more crucial for Faraday's life - he allowed him to read in the books of his bookstore after work. There were two particular books that inspired him: Isaac Watts "The Improvement of the Mind", which probably laid the foundation for Faraday's meticulous way of thinking and working, and the "Conversations on Chemistry" by Miss Marcet, in which two young people Women talk about chemical phenomena. A customer of the bookstore gave him tickets for public lectures by chemistry professor Humphry Davy, which in turn led him to join the City Philosophical Society, a group of young people who listened to scientific evening lectures or who organized and discussed them themselves. Here he acquired his knowledge autodidactically. He wrote it down in notebooks he had created himself, rearranging it independently and also used other ways of presentation. These notes should pave the way for an interesting job for him.

In 1813 Humphry Davy hired him as a laboratory assistant at the Royal Institution in London. The relationship with Davy was not entirely unproblematic, because Ms. Davy from the English upper class paid attention to the carefully maintained distance at the time, while the already recognized chemist Davy appreciated the achievements of his laboratory assistant as independent achievements. Davy took Faraday with him as an assistant on an extensive European tour that included visits to all of the leading chemists and physicists of the time. Back in England (1815) Faraday got a job that would be called a "permanent position" today: he was responsible for the mineralogical collection and the maintenance of the experimental equipment of the Royal Institution of Great Britain. After work and in his free time, Faraday was able to devote himself entirely to his science, because he had obtained a contractual guarantee that he could use the institute's laboratory equipment for this purpose.
In 1821, the year of his marriage to Sarah Barnard (later happily but childlessly married), he was appointed "Superintendent of the House" and was able to move into an official residence in the Royal Institution. In 1825 he was appointed - without ever having studied at a university - on the basis of his numerous successful practical and theoretical studies as director of the Royal Institution and in 1833 as the first Fullerian Professor of Chemistry, one of the few honors Faraday has accepted in his life. He rejected most of the honors. Faraday was well aware of his qualities; however, he felt it was a gift and not a merit. As a professor of chemistry, he worked at the Royal Military Academy in Woolwich from 1830 to 1851 - generations of officers have learned chemistry from him.

While at work, Faraday was ruthless with his own health resources, so that he suffered a severe breakdown at the age of 48. A trip through Switzerland restored his strength, but Faraday's memory increasingly suffered from forgetfulness, which he was able to systematically compensate for in the beginning. At the age of 70 he resigned from his last offices due to his poor memory. He died six years later at his home in Hampton Court Royal Park.


Most of the work at the Royal Institution was commissioned by various clients; they related to mining and mining safety, the effectiveness of lighthouses, steel production and the properties of optical glasses and numerous other areas, and military and civilian reports were also requested. In the course of this research, Faraday discovered a new liquid that was later to be named benzene (see Manufacture of Benzene). It was created during the pyrolysis of Walrat, in a commercially used process for the production of "transportable gas". In addition to the liquefaction of elemental chlorine, this was one of his first and most important chemical works. Since Faraday was a very precise observer - and a very excellent experimenter at that - countless smaller but important inventions in practical life can be traced back to him. He strictly refused to have any of them patented, because he was convinced that they were all based on the laws of nature that God had given all human beings to use. The patenting of the "electromagnetic rotation", Faraday's apparatus and his principle of the electric motor alone could have made him extremely rich. Instead, Werner von Siemens (1816-1892) was able to use his chance and build an industrial empire by patenting the dynamo machine.
Faraday became famous for the cause and description of this electromagnetic phenomenon. The Danish chemist Hans Christian Oersted (1777-1851) discovered electromagnetism in 1821. Faraday carried out in-depth experiments: When electrical current was passed through a ring-shaped arrangement, a magnetic force in circular motion occurred around the wire. Faraday initially called this "electromagnetic rotation". This observation finally led to the discovery of electromagnetic induction in 1831. It was a completely unspectacular observation of a tiny movement - it was enough to let him recognize the full scope of the electromagnetic induction law.
In 1832 the laws of electrolysis followed, also called Faraday's Laws became known. Faraday, who at that time had not yet clearly recognized the difference between voltage and amperage, systematically electrolyzed different solutions and varied amperage, voltage and duration of action and determined the amount of substance produced. Today the laws of electrolysis are formulated as follows:
1. Faraday's law: The amount of substance deposited on the electrodes during electrolysis is proportional to the amount of electricity that has flowed through the electrolyte solution, i.e. the current strength and the duration. The amount of substance is proportional to the charge Q that has passed through the electrolyte solution. Example: The electrolysis of a zinc iodide solution produces twice the amount of zinc if the electrolysis time t or the current I is doubled:

Q = I × t

2. Faraday's law: The amounts of different substances produced by the same amount of electricity in electrolyte solutions are chemically equivalent. To get the amount of substance 1 mole of a substance, one needs the charge:

Q = 1 mol × z × F

Remarks: z is the number of electrons that are exchanged when a particle is formed and F is the Faraday constant 1F = 96485.33289 coulombs per mole.
In 1845 he discovered the one named after him Faraday effectin which the propagation of light is influenced by a magnetic field. To do this, he placed a stick made of heavy lead glass in a wire spool. The plane of oscillation of linearly polarized light rotated when the current flowed through the resulting magnetic field. The discovery was guided by Faraday's belief that heat, light, electricity, and magnetism must be closely related.
Not only is the electrochemistry based on Faraday's work, but also the colloid chemistry. Above all, however, his idea of ​​the electric and magnetic field has been extremely fruitful. Terms used in electrochemistry today such as electrolyte, electrode, ions, anions or cations were coined by Faraday. The electrical unit of capacitance Farad is named after Faraday.
Faraday also found out through experiments that the charge in electrical conductors is only concentrated on the outside. From this, a metal cage could be constructed from a wire mesh, in which the interior is shielded from external electrical fields and electromagnetic waves. Today's car, for example, provides one Faraday cage In the event of a lightning strike, the people inside are not endangered. Today there are numerous other practical uses for this. In the case of coaxial cables for television reception, for example, a sheath made of braided cable protects the inner conductor from interference. Lightning rods use the effect discovered by Faraday of the concentration of charges at exposed points.
Faraday's lectures on the chemical "natural history" of a candle "(Lectures on the Chemical History of a Candle, 1861 - meaning the" development and decay of a candle ") and on" The forces of nature "(" On the various forces of nature and their relations to each other "). These two brilliantly worked out didactic pieces are still used today by didacticians in their lessons in numerous variations.
Recommended literature that can be used in class

  • Bühler / Graf (eds.): Reading texts Chemistry 2 (excerpts from Jane Marcet's book), Stuttgart 2003
  • Faraday, Michael: Natural history of a candle, Bad Salzdethfurth 1980
  • Faraday, Michael: The forces of nature, Bad Salzdethfurth 1984
  • Lemmerich, Jost: Michael Faraday 1971-1867 - researcher of electricity. Munich 1991