Michael Faraday

Faraday c. undefined 1857
Portrait of Faraday in his late thirties, ca. 1826
Michael Faraday, c. 1861, aged about 70
Three Fellows of the Royal Society offering the presidency to Faraday, 1857
Michael Faraday's grave at Highgate Cemetery, London
Equipment used by Faraday to make glass on display at the Royal Institution in London
Electromagnetic rotation experiment of Faraday, ca. 1821
One of Faraday's 1831 experiments demonstrating induction. The liquid battery (right) sends an electric current through the small coil (A). When it is moved in or out of the large coil (B), its magnetic field induces a momentary voltage in the coil, which is detected by the galvanometer (G).
A diagram of Faraday's iron ring-coil apparatus
Built in 1831, the Faraday disk was the first electric generator. The horseshoe-shaped magnet (A) created a magnetic field through the disk (D). When the disk was turned, this induced an electric current radially outward from the center toward the rim. The current flowed out through the sliding spring contact m, through the external circuit, and back into the center of the disk through the axle.
Faraday (right) and John Daniell (left), founders of electrochemistry.
Faraday holding a type of glass bar he used in 1845 to show magnetism affects light in dielectric material.
Michael Faraday meets Father Thames, from Punch (21 July 1855)
Lighthouse lantern room from mid-1800s
Faraday's apparatus for experimental demonstration of ideomotor effect on table-turning
Faraday delivering a Christmas Lecture at the Royal Institution in 1856.
Statue of Faraday in Savoy Place, London. Sculptor John Henry Foley RA.
Plaque erected in 1876 by the Royal Society of Arts at 48 Blandford Street, Marylebone, London
Chemische Manipulation, 1828
Michael Faraday in his laboratory, c. 1850s.
Michael Faraday's study at the Royal Institution.
Michael Faraday's flat at the Royal Institution.
Artist Harriet Jane Moore who documented Faraday's life in watercolours.

English scientist who contributed to the study of electromagnetism and electrochemistry.

- Michael Faraday

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Benzene

Organic chemical compound with the molecular formula C6H6.

Kekulé's 1872 modification of his 1865 theory, illustrating rapid alternation of double bonds Critics pointed out a problem with Kekulé's original (1865) structure for benzene: Whenever benzene underwent substitution at the ortho position, two distinguishable isomers should have resulted, depending on whether a double bond or a single bond existed between the carbon atoms to which the substituents were attached; however, no such isomers were observed.  In 1872, Kekulé suggested that benzene had two complementary structures and that these forms rapidly interconverted, so that if there were a double bond between any pair of carbon atoms at one instant, that double bond would become a single bond at the next instant (and vice versa).  To provide a mechanism for the conversion process, Kekulé proposed that the valency of an atom is determined by the frequency with which it collided with its neighbors in a molecule.  As the carbon atoms in the benzene ring collided with each other, each carbon atom would collide twice with one neighbor during a given interval and then twice with its other neighbor during the next interval.  Thus, a double bond would exist with one neighbor during the first interval and with the other neighbor during the next interval.  Therefore, between the carbon atoms of benzene there were no fixed (i.e., constant) and distinct single or double bonds; instead, the bonds between the carbon atoms were identical.  See pages 86–89  of Auguste Kekulé (1872) "Ueber einige Condensationsprodukte des Aldehyds" (On some condensation products of aldehydes), Liebig's Annalen der Chemie und Pharmacie, 162(1): 77–124, 309–320.  From p. 89:  "Das einfachste Mittel aller Stöße eines Kohlenstoffatoms ergiebt sich aus der Summe der Stöße der beiden ersten Zeiteinheiten, die sich dann periodisch wiederholen.  … man sieht daher, daß jedes Kohlenstoffatom mit den beiden anderen, … daß diese Verschiedenheit nur eine scheinbare, aber keine wirkliche ist." (The simplest average of all the collisions of a carbon atom [in benzene] comes from the sum of the collisions during the first two units of time, which then periodically repeat.  … thus one sees that each carbon atom collides equally often with the two others against which it bumps, [and] thus stands in exactly the same relation with its two neighbors.  The usual structural formula for benzene expresses, of course, only the collisions that occur during one unit of time, thus during one phase, and so one is led to the view [that] doubly substituted derivatives [of benzene] must be different at positions 1,2 and 1,6 [of the benzene ring].  If the idea [that was] just presented—or a similar one—can be regarded as correct, then [it] follows therefrom that this difference [between the bonds at positions 1,2 and 1,6] is only an apparent [one], not a real [one].)
Historic benzene structures (from left to right) by Claus (1867), Dewar (1867), Ladenburg (1869), Armstrong (1887), Thiele (1899) and Kekulé (1865). Dewar benzene and prismane are distinct molecules that have Dewar's and Ladenburg's structures. Thiele and Kekulé's structures are used today.
The various representations of benzene.
Friedel-Crafts acylation of benzene by acetyl chloride
A bottle of benzene. The warnings show benzene is a toxic and flammable liquid.

Michael Faraday first isolated and identified benzene in 1825 from the oily residue derived from the production of illuminating gas, giving it the name bicarburet of hydrogen.

Ernest Rutherford

New Zealand physicist who came to be known as the father of nuclear physics.

Ernest Rutherford
Rutherford in 1892, aged 21
Lord Rutherford's grave in Westminster Abbey
Ernest Rutherford at McGill University in 1905
Top: Expected results: alpha particles passing through the plum pudding model of the atom undisturbed. 
Bottom: Observed results: a small portion of the particles were deflected, indicating a small, concentrated charge. Diagram is not to scale; in reality the nucleus is vastly smaller than the electron shell.
A plaque commemorating Rutherford's presence at the University of Manchester
nitrogen plasma
A statue of a young Ernest Rutherford at his memorial in Brightwater, New Zealand.
A Russian postage depicting Scattering diagram
Radioaktive Substanzen und ihre Strahlungen, 1913

Encyclopædia Britannica considers him to be the greatest experimentalist since Michael Faraday (1791–1867).

Ion

Atom or molecule with a net electrical charge.

Hydrogen atom (center) contains a single proton and a single electron. Removal of the electron gives a cation (left), whereas the addition of an electron gives an anion (right). The hydrogen anion, with its loosely held two-electron cloud, has a larger radius than the neutral atom, which in turn is much larger than the bare proton of the cation. Hydrogen forms the only charge-+1 cation that has no electrons, but even cations that (unlike hydrogen) retain one or more electrons are still smaller than the neutral atoms or molecules from which they are derived.
Schematic of an ion chamber, showing drift of ions. Electrons drift faster than positive ions due to their much smaller mass.
Avalanche effect between two electrodes. The original ionization event liberates one electron, and each subsequent collision liberates a further electron, so two electrons emerge from each collision: the ionizing electron and the liberated electron.
Equivalent notations for an iron atom (Fe) that lost two electrons, referred to as ferrous.
Mixed Roman numerals and charge notations for the uranyl ion. The oxidation state of the metal is shown as superscripted Roman numerals, whereas the charge of the entire complex is shown by the angle symbol together with the magnitude and sign of the net charge.
An electrostatic potential map of the nitrate ion . The 3-dimensional shell represents a single arbitrary isopotential.

This term was introduced (after a suggestion by the English polymath William Whewell) by English physicist and chemist Michael Faraday in 1834 for the then-unknown species that goes from one electrode to the other through an aqueous medium.

Electrode

Electrical conductor used to make contact with a nonmetallic part of a circuit .

Electrodes used in shielded metal arc welding
Schematic of a voltaic (galvanic) cell
Various disposable batteries: two 9-volt, two "AAA", two "AA", and one each of "C", "D", a cordless phone battery, a camcorder battery, a 2-meter handheld ham radio battery, and a button battery.
Rechargeable Batteries
Electric current and electrons directions for a secondary battery during discharge and charge.
Potential energy surface for the donor and the acceptor as.
A typical flow battery consists of two tanks of liquids which are pumped past a membrane held between two electrodes.

A term coined by William Whewell at Faraday's request, derived from the Greek words ἄνο (ano) δος, 'upwards' and ὁδός (hodós), 'a way'.

Electromagnetism

Branch of physics involving the study of the electromagnetic force, a type of physical interaction that occurs between electrically charged particles.

Aurora at Alaska showing light created by charged particles and magnetism, fundamental concepts to electromagnetism study
Hans Christian Ørsted
André-Marie Ampère
James Clerk Maxwell
Representation of the electric field vector of a wave of circularly polarized electromagnetic radiation.
Magnetic reconnection in the solar plasma gives rise to solar flares, a complex magnetohydrodynamical phenomenon.

This unification, which was observed by Michael Faraday, extended by James Clerk Maxwell, and partially reformulated by Oliver Heaviside and Heinrich Hertz, is one of the key accomplishments of 19th-century mathematical physics.

Capacitance

Ratio of the amount of electric charge stored on a conductor to a difference in electric potential.

An Andeen-Hagerling 2700A capacitance bridge

The SI unit of capacitance is the farad (symbol: F), named after the English physicist Michael Faraday.

Cathode

Electrode from which a conventional current leaves a polarized electrical device.

Diagram of a copper cathode in a galvanic cell (e.g., a battery). Positively charged cations move towards the cathode allowing a positive current i to flow out of the cathode.
Glow from the directly heated cathode of a 1 kW power tetrode tube in a radio transmitter. The cathode filament is not directly visible
Schematic symbol used in circuit diagrams for vacuum tube, showing cathode
Cold cathode (lefthand electrode) in neon lamp

The word was coined in 1834 from the Greek κάθοδος (kathodos), 'descent' or 'way down', by William Whewell, who had been consulted by Michael Faraday over some new names needed to complete a paper on the recently discovered process of electrolysis.

Royal Institution

Organisation for scientific education and research, based in the City of Westminster.

The Royal Institution building on Albemarle Street, London, c. 1838.
A Friday Evening Discourse at the Royal Institution; Sir James Dewar on Liquid Hydrogen by Henry Jamyn Brooks, 1904
Michael Faraday's 1856 Christmas Lecture
The exterior of the Royal Institution in 2011
The Royal Institution Lecture Theatre. Here Michael Faraday first demonstrated electromagnetism.
Royal Institution. Faraday Museum. Faraday's original 1850s laboratory

The most famous of these are the annual Royal Institution Christmas Lectures, founded by Michael Faraday in 1825.

Electric motor

Electrical machine that converts electrical energy into mechanical energy.

Animation showing operation of a brushed DC electric motor.
Cutaway view through stator of induction motor.
Faraday's electromagnetic experiment, 1821
Jedlik's "electromagnetic self-rotor", 1827 (Museum of Applied Arts, Budapest). The historic motor still works perfectly today.
An electric motor presented to Kelvin by James Joule in 1842, Hunterian Museum, Glasgow
Electric motor rotor (left) and stator (right)
Salient-pole rotor
Commutator in a universal motor from a vacuum cleaner. Parts: (A) commutator, (B) brush
Workings of a brushed electric motor with a two-pole rotor and PM stator. ("N" and "S" designate polarities on the inside faces of the magnets; the outside faces have opposite polarities.)
A: shunt B: series C: compound f = field coil
6/4 pole switched reluctance motor
Modern low-cost universal motor, from a vacuum cleaner. Field windings are dark copper-colored, toward the back, on both sides. The rotor's laminated core is gray metallic, with dark slots for winding the coils. The commutator (partly hidden) has become dark from use; it is toward the front. The large brown molded-plastic piece in the foreground supports the brush guides and brushes (both sides), as well as the front motor bearing.
Large 4,500 hp AC induction motor.
A miniature coreless motor
A stepper motor with a soft iron rotor, with active windings shown. In 'A' the active windings tend to hold the rotor in position. In 'B' a different set of windings are carrying a current, which generates torque and rotation.

The first demonstration of the effect with a rotary motion was given by Michael Faraday in 1821.

Farad

SI derived unit of electrical capacitance, the ability of a body to store an electrical charge.

A one farad modern super-capacitor. The scale behind is in inches (top) and centimetres (bottom).
Examples of different types of capacitors

It is named after the English physicist Michael Faraday (1791-1867).