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Quantization Of Charge
The elementary charge, usually denoted by , is a fundamental physical constant, defined as the electric charge Charge carrier, carried by a single proton (+1 ''e'') or, equivalently, the magnitude of the negative electric charge carried by a single electron, which has charge −1 . In International System of Units, SI units, the coulomb is defined such that the value of the elementary charge is exactly or 160.2176634 Orders of magnitude (numbers)#10−21, zeptocoulombs (zC). Since the 2019 revision of the SI, the seven SI base units are defined in terms of seven fundamental physical constants, of which the elementary charge is one. In the centimetre–gram–second system of units (CGS), the corresponding quantity is . Robert Andrews Millikan, Robert A. Millikan and Harvey Fletcher's oil drop experiment first directly measured the magnitude of the elementary charge in 1909, differing from the modern accepted value by just 0.6%. Under assumptions of the then-disputed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physical Constant
A physical constant, sometimes fundamental physical constant or universal constant, is a physical quantity that cannot be explained by a theory and therefore must be measured experimentally. It is distinct from a mathematical constant, which has a fixed numerical value, but does not directly involve any physical measurement. There are many physical constants in science, some of the most widely recognized being the speed of light in vacuum ''c'', the gravitational constant ''G'', the Planck constant ''h'', the electric constant ''ε''0, and the elementary charge ''e''. Physical constants can take many dimensional forms: the speed of light signifies a maximum speed for any object and its dimension is length divided by time; while the proton-to-electron mass ratio is dimensionless. The term "fundamental physical constant" is sometimes used to refer to universal-but-dimensioned physical constants such as those mentioned above. Increasingly, however, physicists reserve the expressi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CODATA
The Committee on Data of the International Science Council (CODATA) was established in 1966 as the Committee on Data for Science and Technology, originally part of the International Council of Scientific Unions, now part of the International Science Council (ISC). Since November 2023 its president is the Catalan researcher Mercè Crosas. CODATA exists to promote global collaboration to advance open science and to improve the availability and usability of data for all areas of research. CODATA supports the principle that data produced by research and susceptible to being used for research should be as open as possible and as closed as necessary. CODATA works also to advance the interoperability and the usability of such data; research data should be FAIR (findable, accessible, interoperable and reusable). By promoting the policy, technological, and cultural changes that are essential to promote open science, CODATA helps advance ISC's vision and mission of advancing science as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Natural Units
In physics, natural unit systems are measurement systems for which selected physical constants have been set to 1 through nondimensionalization of physical units. For example, the speed of light may be set to 1, and it may then be omitted, equating mass and energy directly rather than using as a conversion factor in the typical mass–energy equivalence equation . A purely natural system of units has all of its dimensions collapsed, such that the physical constants completely define the system of units and the relevant physical laws contain no conversion constants. While natural unit systems simplify the form of each equation, it is still necessary to keep track of the non-collapsed dimensions of each quantity or expression in order to reinsert physical constants (such dimensions uniquely determine the full formula). Systems of natural units Summary table where: * is the fine-structure constant ( ≈ 0.007297) * ≈ * ≈ * A dash (—) indicates where the system ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atomic Units
The atomic units are a system of natural units of measurement that is especially convenient for calculations in atomic physics and related scientific fields, such as computational chemistry and atomic spectroscopy. They were originally suggested and named by the physicist Douglas Hartree. Atomic units are often abbreviated "a.u." or "au", not to be confused with similar abbreviations used for astronomical units, arbitrary units, and absorbance units in other contexts. Motivation In the context of atomic physics, using the atomic units system can be a convenient shortcut, eliminating symbols and numbers and reducing the order of magnitude of most numbers involved. For example, the Hamiltonian operator in the Schrödinger equation for the helium atom with standard quantities, such as when using SI units, is : \hat = - \frac \nabla_1^2 - \frac \nabla_2^2 - \frac - \frac + \frac , but adopting the convention associated with atomic units that transforms quantities into dimensionl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Avogadro Constant
The Avogadro constant, commonly denoted or , is an SI defining constant with an exact value of when expressed in reciprocal moles. It defines the ratio of the number of constituent particles to the amount of substance in a sample, where the particles in question are any designated elementary entity, such as molecules, atoms, ions, ion pairs. The numerical value of this constant is known as the Avogadro number, commonly denoted . The Avogadro ''number'' is an exact number equal to the number of constituent particles in one mole of any substance (by definition of the mole), historically derived from the experimental determination of the number of atoms in 12 grams of carbon-12 (12C) before the 2019 revision of the SI. Both the constant and the number are named after the Italian physicist and chemist Amedeo Avogadro. The Avogadro constant is used as a proportionality factor in relating the ''amount of substance'' , in a sample of a substance , to the corresponding n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Johann Josef Loschmidt
Johann Josef Loschmidt (15 March 1821 – 8 July 1895), better known as Josef Loschmidt, was an Austrian scientist who performed ground-breaking work in chemistry, physics (thermodynamics, optics, electrodynamics), and crystal forms. Born in Karlsbad, a town in the Austrian Empire (now Karlovy Vary, Czech Republic), Loschmidt became professor of physical chemistry at the University of Vienna in 1868. He had two early mentors. The first was Bohemian priest Adalbert Czech, who persuaded Loschmidt's parents to send young Josef to high school in the Piarist monastery in Schlackenwerth and, in 1837, to advanced high-school classes in Prague. This was followed by two years of philosophy and mathematics at Prague's Charles University, where Loschmidt met his second important mentor. This was philosophy professor Franz Serafin Exner, whose eyesight was failing, and who asked Loschmidt to be his personal reader. Exner was known for his innovative school reforms, which included promoti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Faraday Constant
In physical chemistry, the Faraday constant (symbol , sometimes stylized as ℱ) is a physical constant defined as the quotient of the total electric charge () by the amount () of elementary charge carriers in any given sample of matter: it is expressed in units of coulombs per mole (C/mol). As such, it represents the " molar elementary charge", that is, the electric charge of one mole of elementary carriers (e.g., protons). It is named after the English scientist Michael Faraday. Since the 2019 revision of the SI, the Faraday constant has an exactly defined value, the product of the elementary charge (, in coulombs) and the Avogadro constant (, in reciprocal moles): : Derivation The Faraday constant can be thought of as the proportionality factor between the charge in coulombs (used in physics and in practical electrical measurements) and the amount of substance in moles (used in chemistry), and is therefore of particular use in electrochemistry, particularly in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Max Planck
Max Karl Ernst Ludwig Planck (; ; 23 April 1858 – 4 October 1947) was a German Theoretical physics, theoretical physicist whose discovery of energy quantum, quanta won him the Nobel Prize in Physics in 1918. Planck made many substantial contributions to theoretical physics, but his fame as a physicist rests primarily on his role as the originator of Quantum mechanics, quantum theory and one of the founders of modern physics, which revolutionized understanding of atomic and Subatomic particle, subatomic processes. He is known for the Planck constant, which is of foundational importance for quantum physics, and which he used to derive a set of Unit of measurement, units, today called Planck units, expressed only in terms of fundamental physical constants. Planck was twice president of the German scientific institution Kaiser Wilhelm Society. In 1948, it was renamed the Max Planck Society (Max-Planck-Gesellschaft) and nowadays includes 83 institutions representing a wide range ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Planck%27s Law Of Black-body Radiation
Max Karl Ernst Ludwig Planck (; ; 23 April 1858 – 4 October 1947) was a German theoretical physicist whose discovery of energy quanta won him the Nobel Prize in Physics in 1918. Planck made many substantial contributions to theoretical physics, but his fame as a physicist rests primarily on his role as the originator of quantum theory and one of the founders of modern physics, which revolutionized understanding of atomic and subatomic processes. He is known for the Planck constant, which is of foundational importance for quantum physics, and which he used to derive a set of units, today called Planck units, expressed only in terms of fundamental physical constants. Planck was twice president of the German scientific institution Kaiser Wilhelm Society. In 1948, it was renamed the Max Planck Society (Max-Planck-Gesellschaft) and nowadays includes 83 institutions representing a wide range of scientific directions. Early life and education Planck came from a traditional, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atomic Theory
Atomic theory is the scientific theory that matter is composed of particles called atoms. The definition of the word "atom" has changed over the years in response to scientific discoveries. Initially, it referred to a hypothetical concept of there being some fundamental particle of matter, too small to be seen by the naked eye, that could not be divided. Then the definition was refined to being the basic particles of the chemical elements, when chemists observed that elements seemed to combine with each other in ratios of small whole numbers. Then physicists discovered that these particles had an internal structure of their own and therefore perhaps did not deserve to be called "atoms", but renaming atoms would have been impractical by that point. Atomic theory is one of the most important scientific developments in history, crucial to all the physical sciences. At the start of ''The Feynman Lectures on Physics'', physicist and Nobel laureate Richard Feynman offers the atomic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oil Drop Experiment
The oil drop experiment was performed by Robert Andrews Millikan, Robert A. Millikan and Harvey Fletcher in 1909 to measure the Elementary charge, elementary electric charge (the charge of the electron). The experiment took place in the Ryerson Physical Laboratory at the University of Chicago. Millikan received the Nobel Prize in Physics in 1923. The experiment observed tiny electrically charged droplets of oil located between two parallel metal surfaces, forming the plates of a capacitor. The plates were oriented horizontally, with one plate above the other. A mist of atomizer nozzle, atomized oil drops was introduced through a small hole in the top plate; some would be ionization, ionized naturally. First, with zero applied electric field, the velocity of a falling droplet was measured. At terminal velocity, the drag (physics), drag force equals the gravity, gravitational force. As both forces depend on the radius in different ways, the radius of the droplet, and therefore the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Harvey Fletcher
Harvey Fletcher (September 11, 1884 – July 23, 1981) was an American physicist. Known as the "father of stereophonic sound", he is credited with the invention of the 2-A audiometer and an early electronic hearing aid. He was an investigator into the nature of speech and hearing, and made contributions in acoustics, electrical engineering, speech, medicine, music, atomic physics, sound pictures, and education. Following his death, he was credited with collaborating with his doctoral advisor, Robert Millikan, on the Nobel-prize winning oil drop experiment which first determined the charge of the electron. Early years Fletcher was born in Provo, Utah. He graduated from Brigham Young High School in 1904. He enrolled at Brigham Young University (BYU), graduating in 1907 with a bachelor's degree. He married Lorena Chipman. They were the parents of seven children. Harvey Fletcher was the father of James C. Fletcher, former president of the University of Utah and NASA Administrator ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
