Michael FaradayBritish physicist and chemist
Michael Faraday, (born September 22, 1791, Newington, Surrey, England—died August 25, 1867, Hampton Court, Surrey), English physicist and chemist whose many experiments contributed greatly to the understanding of electromagnetism.
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Michael Faraday, (born September 22, 1791, Newington, Surrey, England—died August 25, 1867, Hampton Court, Surrey), English physicist and chemist whose many experiments contributed greatly to the understanding of electromagnetism.
Faraday, who became one of the greatest scientists of the 19th century, began his career as a chemist. He wrote a manual of practical chemistry that reveals his mastery of the technical aspects of his art, discovered a number of new organic compounds, among them benzene, and was the first to liquefy a “permanent” gas (i.e., one that was believed to be incapable of liquefaction). His major contribution, however, was in the field of electricity and magnetism. He was the first to produce an electric current from a magnetic field, invented the first electric motor and dynamo, demonstrated the relation between electricity and chemical bonding, discovered the effect of magnetism on light, and discovered and named diamagnetism, the peculiar behaviour of certain substances in strong magnetic fields. He provided the experimental, and a good deal of the theoretical, foundation upon which James Clerk Maxwell erected classical electromagnetic field theory.
Education and Early LifeMichael Faraday was born on September 22, 1791 in London, England, UK. He was the third child of James and Margaret Faraday. His father was a blacksmith who had poor health. Before marriage, his mother had been a servant. The family lived in a degree of poverty.
Michael Faraday attended a local school until he was 13, where he received a basic education. To earn money for the family he started working as a delivery boy for a bookshop. He worked hard and impressed his employer. After a year, he was promoted to become an apprentice bookbinder.
Michael Faraday was eager to learn more about the world; he did not restrict himself to binding the shop’s books. After working hard each day, he spent his free time reading the books he had bound.
Two books in particular captivated him:
The Encyclopedia Britannica – his source for electrical knowledge and much more
Conversations on Chemistry – 600 pages of chemistry for ordinary people written by Jane Marcet
Faraday’s education took another step upward when William Dance, a customer of the bookshop, asked if he would like tickets to hear Sir Humphry Davy lecturing at the Royal Institution.
Sir Humphry Davy was one of the most famous scientists in the world. Faraday jumped at the chance and attended four lectures about one of the newest problems in chemistry – defining acidity.
At this time Faraday had begun more sophisticated experiments at the back of the bookshop, building an electric battery using copper coins and zinc discs separated by moist, salty paper. He used his battery to decompose chemicals such as magnesium sulfate.
The article on electricity in the third edition of the Encyclopædia Britannica particularly fascinated him. Using old bottles and lumber, he made a crude electrostatic generator and did simple experiments. He also built a weak voltaic pile with which he performed experiments in electrochemistry.
Michael Faraday’s Career at the Royal InstitutionFaraday began work at the Royal Institution of Great Britain at the age of 21 on March 1, 1813.
He was destined to be associated with the Royal Institution for 54 years, ending up as a Professor of Chemistry.
Faraday’s job as a chemical assistant was to prepare apparatus for the experiments and the lectures at the Royal Institution.
At first, this involved working with nitrogen trichloride, the explosive which had already injured Davy. Faraday himself was knocked unconscious briefly by another nitrogen chloride explosion, and then Davy was injured again, finally (thankfully) putting to an end to work with that particular substance.
After just seven months at the Royal Institution, Davy took Faraday as his secretary on a tour of Europe that lasted 18 months.
In 1816, aged 24, Faraday gave his first ever lecture, on the properties of matter, to the City Philosophical Society. And he published his first ever academic paper, discussing his analysis of calcium hydroxide, in the Quarterly Journal of Science.
In 1821, aged 29, he was promoted to be Superintendent of House and Laboratory of the Royal Institution. He also married Sarah Barnard. He and his bride lived in rooms in the Royal Institution for most of the next 46 years: no longer in attic rooms; they now lived in a comfortable suite Humphry Davy himself had once lived in.
In 1824, aged 32, he was elected to the Royal Society. This was recognition that he had become a notable scientist in his own right.
In 1825, aged 33, he became Director of the Royal Institution’s Laboratory.
In 1833, aged 41, he became Fullerian Professor of Chemistry at the Royal Institution of Great Britain. He held this position for the rest of his life.
In 1848, aged 54, and again in 1858 he was offered the Presidency of the Royal Society, but he turned it down.
Michael Faraday’s Scientific Achievements and Discoveries
In Faraday’s lifetime people had started to use the word physicist, Faraday disliked the word and always described himself as a philosopher.
He was a man devoted to discovery through experimentation, and he was famous for never giving up on ideas which came from his scientific intuition.
If he thought an idea was a good one, he would keep experimenting through multiple failures until he got what he expected; or until he finally decided that mother nature had shown his intuition to be wrong – but in Faraday’s case, this was rare.
Here are some of his most notable discoveries:
1821: Discovery of Electromagnetic RotationThis is a glimpse of what would eventually develop into the electric motor, based on Hans Christian Oersted’s discovery that a wire carrying electric current has magnetic properties.
The Faraday Motor (The Homopolar Motor)It has been argued that galaxies might behave like a device invented by Michael Faraday,the Homopolar Motor. A Homopolar Motor is driven by magnetic fields induced in a circular, ridgid conductive metal plate. The metal plate is placed between the poles of an electromagnet, causing it to spin at a steady rate
proportional to the input current. The meter attached to the wall in most backyards that determines monthly electric bills is a Homopolar motor.
Faraday’s electromagnetic rotation apparatus. Electricity flows through the wires. The liquid in the cups is mercury, a good conductor of electricity. In the cup on the right, the metal wire continuously rotates around the central magnet as long as electric current is flowing through the circuit.
1823: Gas Liquefaction and Refrigeration
In 1802 John Dalton had stated his belief that all gases could be liquified by the use of low temperatures and/or high pressures. Faraday provided hard evidence for Dalton’s belief by applying pressure to liquefy chlorine gas and ammonia gas for the first time.
Showing that ammonia could be liquefied under pressure, then evaporated to cause cooling, led to commercial refrigeration .
The ammonia liquefaction was of further interest, because Faraday observed that when he allowed the ammonia to evaporate again, it caused cooling.The principle of cooling by artificial evaporation had been demonstrated publicly by William Cullen in Edinburgh in 1756. Cullen had used a pump to reduce the pressure above a flask of ether, causing the ether to evaporate quickly. The evaporation caused cooling, and ice formed on the outside of the flask as moisture from the air came into contact with it.The importance of Faraday’s discovery was that he had shown that mechanical pumps could transform a gas at room temperature into a liquid. The liquid could then be evaporated, cooling its surroundings and the resulting gas could be collected and compressed by a pump into a liquid again, then the whole cycle could be repeated. This is the basis of how modern refrigerators and freezers work.In 1862 Ferdinand Carré demonstrated the world’s first commercial ice-making machine at the Universal London Exhibition. The machine used ammonia as its coolant and produced ice at the rate of 200 kg per hour.
1825: Discovery of BenzeneHistorically, benzene is one of the most important substances in chemistry, both in a practical sense – i.e. making new materials; and in a theoretical sense – i.e. understanding chemical bonding. Michael Faraday discovered benzene in the oily residue left behind from producing gas for lighting in London
A model of a benzene molecule
1831: Discovery of Electromagnetic InductionThis was an enormously important discovery for the future of both science and technology. Faraday discovered that a varying magnetic field causes electricity to flow in an electric circuit.
For example, moving a horseshoe magnet over a wire produces an electric current, because the movement of the magnet causes a varying magnetic field.
Previously, people had only been able to produce electric current with a battery. Now Faraday had shown that movement could be turned into electricity – or in more scientific language, kinetic energy could be converted to electrical energy.
Most of the power in our homes today is produced using this principle. Rotation (kinetic energy) is converted into electricity using electromagnetic induction. The rotation can be produced by high pressure steam from coal, gas, or nuclear energy turning turbines; or by hydroelectric plants; or by wind-turbines, for example.
1834: Faraday’s Laws of ElectrolysisFaraday was one of the major players in the founding of the new science of electrochemistry. This is the science of understanding what happens at the interface of an electrode with an ionic substance. Electrochemistry is the science that has produced the Li ion batteries and metal hydride batteries capable of powering modern mobile technology. Faraday’s laws are vital to our understanding of electrode reactions:
Statements of the laws Faraday's 1st Law of Electrolysis - "The mass of a substance altered at an electrode during
electrolysis is directly proportional to the quantity of electricity transferred at that electrode. Quantity of electricity refers to the quantity of electrical charge, typically measured in coulomb."
Faraday's 2nd Law of Electrolysis - "For a given quantity of D.C electricity (electric charge), the mass of an elemental material altered at an electrode is directly proportional to the element's equivalent weight". The equivalent weight of a substance is equal to its molar mass divided by the change in oxidation state it undergoes upon electrolysis (often equal to its charge or valence).
Mathematical formFaraday's laws can be summarized by
m=(QF
)(Mz
)
where:
m is the mass of the substance liberated at an electrode in grams Q is the total electric charge passed through the substance F = 96485 C mol−1 is the Faraday constant M is the molar mass of the substance z is the valency number of ions of the substance (electrons transferred per ion).
Note that M/z is the same as the equivalent weight of the substance altered.
For Faraday's first law, M, F, and z are constants, so that the larger the value of Q the larger m will be.
For Faraday's second law, Q, F, and z are constants, so that the larger the value of M/z (equivalent weight) the larger m will be.
In the simple case of constant-current electrolysis, Q = I t leading to
m=( ¿F
)(Mz
)
and then to
n=( ¿F
)¿
where:
n is the amount of substance ("number of moles") liberated: n = m/M t is the total time the constant current was applied.
In the more complicated case of a variable electric current, the total charge Q is the electric currentI(\τ) integrated over time \τ)
Q=∫o
t
(Iτ )dτ
Here t is the total electrolysis time.
1836: Invention of the Faraday CageFaraday discovered that when an electrical conductor becomes charged, all of the extra charge sits on the outside of the conductor. This means that the extra charge does not appear on the inside of a room or cage made of metal. In addition to offering protection for people, sensitive electrical or electrochemical experiments can be placed inside a Faraday Cage to prevent interference from external electrical activity.Faraday cages can also create dead zones for mobile communication
1845: Discovery of the Faraday Effect – a magneto-optical effect
This was another vital experiment in the history of science, the first to link electromagnetism and light – a link finally described fully by James Clerk Maxwell’s equations in 1864, which established that light is an electromagnetic wave.Faraday discovered that a magnetic field causes the plane of light polarization to rotate.
1845: Discovery of Diamagnetism as a Property of all MatterFaraday discovered that all substances are diamagnetic – most are weakly so – some are strongly so.Diamagnetism opposes the direction of an applied magnetic field.For example, if you held the north pole of a magnet near a strongly diamagnetic substance, this substance would be pushed away by the magnet.Diamagnetism in materials, induced by very strong modern magnets, can be used to produce levitation. Even living things, such as frogs, are diamagnetic – and can be levitated in a strong magnetic field.
The Faraday Disc GeneratorThe purpose of these experimental investigations was to research, design & build a traditional two-piece Faraday disc generator for physics demonstrations. The design is based on the models that follow Sir Michael Faraday 's original 1831 disc dynamo very closely.
Faraday’s BooksFaraday's books, with the exception of Chemical Manipulation, were collections of scientific papers or transcriptions of lectures. Since his death, Faraday's diary has been published, as have several large volumes of his letters and Faraday's journal from his travels with Davy in 1813–1815.
A Chemical History of a Candle
Experimental Researches in Electricity The Forces of Matter A course of six lectures on the various forces of matter, and their relations to each other On The Various Forces Of Nature The Letters of Faraday and Schoenbein, 1836-1862, with Notes, Comments and References to
Contemporary Letters.Lavoisier; Fourier; Faraday (Great Books of the Western World, Vol 45) by Michael Faraday, Jean Baptiste Joseph Fourier, Antoine Laurent Lavoisier, Robert Maynard Hutchins
Lectures on the Physical Forces
Later lifeIn June 1832, the University of Oxford granted Faraday a Doctor of Civil Law degree (honorary). During his lifetime, he was offered a knighthood in recognition for his services to science, which he turned down on religious grounds, believing it was against the word of the Bible to accumulate riches and pursue worldly reward, stating he preferred to remain "plain Mr Faraday to the end". He twice refused to become President of the Royal Society.He was elected a foreign member of the Royal Swedish Academy of Sciences in 1838, and was one of eight foreign members elected to the French Academy of Sciences in 1844. In 1849 he was elected as associated member to the Royal Institute of the Netherlands, which two years later became the Royal Netherlands Academy of Arts and Sciences and he was subsequently made foreign member.
Faraday died at his house at Hampton Court on 25 August 1867, aged 75.[25] He had previously turned down burial in Westminster Abbey, but he has a memorial plaque there, near Isaac Newton's tomb. Faraday was interred in the dissenters' (non-Anglican) section of Highgate Cemetery.
