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Gauss (unit)
The gauss, symbol (sometimes Gs), is a unit of measurement of magnetic induction, also known as '' magnetic flux density''. The unit is part of the Gaussian system of units, which inherited it from the older CGS-EMU system. It was named after the German mathematician and physicist Carl Friedrich Gauss in 1936. One gauss is defined as one maxwell per square centimetre. As the cgs system has been superseded by the International System of Units (SI), the use of the gauss has been deprecated by the standards bodies, but is still regularly used in various subfields of science. The SI unit for magnetic flux density is the tesla (symbol T), which corresponds to . Name, symbol, and metric prefixes Albeit not a component of the International System of Units, the usage of the gauss generally follows the rules for SI units. Since the name is derived from a person's name, its symbol is the uppercase letter ''G''. When the unit is spelled out, it is written in lowercase ("gauss"), unless ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gaussian Units
Gaussian units constitute a metric system of physical units. This system is the most common of the several electromagnetic unit systems based on cgs (centimetre–gram–second) units. It is also called the Gaussian unit system, Gaussian-cgs units, or often just cgs units. The term "cgs units" is ambiguous and therefore to be avoided if possible: there are several variants of cgs with conflicting definitions of electromagnetic quantities and units. SI units predominate in most fields, and continue to increase in popularity at the expense of Gaussian units. Alternative unit systems also exist. Conversions between quantities in Gaussian and SI units are direct unit conversions, because the quantities themselves are defined differently in each system. This means that the equations expressing physical laws of electromagnetism—such as Maxwell's—will change depending on the system of units employed. As an example, quantities that are dimensionless in one system may have dimension ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oersted
The oersted (symbol Oe) is the coherent derived unit of the auxiliary magnetic field H in the centimetre–gram–second system of units (CGS). It is equivalent to 1 dyne per maxwell. Difference between CGS and SI systems In the CGS system, the unit of the H-field is the oersted and the unit of the B-field is the gauss. In the SI system, the unit ampere per meter (A/m), which is equivalent to newton per weber, is used for the H-field and the unit of tesla is used for the B-field. History The unit was established by the IEC in the 1930s in honour of Danish physicist Hans Christian Ørsted. Ørsted discovered the connection between magnetism and electric current when a magnetic field produced by a current-carrying copper bar deflected a magnetised needle during a lecture demonstration. Definition The oersted is defined as a dyne per unit pole. The oersted is (≈) amperes per meter, in terms of SI units. The H-field strength inside a long solenoid wound with 79.58 turn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Refrigerator Magnet
A refrigerator magnet or fridge magnet is a small magnet, often attached to an artistic or whimsical ornament, which may be used to post items such as shopping lists, Christmas cards, child art or reminders on a refrigerator door, or which simply serves as decoration. Refrigerator magnets come in a wide variety of shapes and sizes, and may have promotional messages placed on them. In addition to refrigerators, fridge magnets are commonly placed on steel-backed whiteboards and bulletin boards, as well as other metal furniture such as filing cabinets and tool chests. Refrigerator magnets are popular souvenir and collectible objects. Manufacture The first fridge magnets were cylindrical or solid rectangular magnets. Later, a flexible magnet was developed, composed of a high-coercivity ferrimagnetic or ferromagnetic compound (usually barium ferrite) mixed with a plastic binder. This is extruded as a sheet and passes on a conveyor belt over a line of powerful cylindrical permane ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earth's Outer Core
Earth's outer core is a fluid layer about thick, composed of mostly iron and nickel that lies above Earth's solid inner core and below its mantle. The outer core begins approximately beneath Earth's surface at the core-mantle boundary and ends beneath Earth's surface at the inner core boundary. Properties Unlike Earth's solid, inner core, its outer core is liquid. Evidence for a fluid outer core includes seismology which shows that seismic shear-waves are not transmitted through the outer core. Although having a composition similar to Earth's solid inner core, the outer core remains liquid as there is not enough pressure to keep it in a solid state. Seismic inversions of body waves and normal modes constrain the radius of the outer core to be 3483 km with an uncertainty of 5 km, while that of the inner core is 1220±10 km. Estimates for the temperature of the outer core are about in its outer region and near the inner core. Modeling has shown that the outer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jupiter
Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousandth the mass of the Sun. Jupiter is the third brightest natural object in the Earth's night sky after the Moon and Venus, and it has been observed since prehistoric times. It was named after the Roman god Jupiter, the king of the gods. Jupiter is primarily composed of hydrogen, but helium constitutes one-quarter of its mass and one-tenth of its volume. It probably has a rocky core of heavier elements, but, like the other giant planets in the Solar System, it lacks a well-defined solid surface. The ongoing contraction of Jupiter's interior generates more heat than it receives from the Sun. Because of its rapid rotation, the planet's shape is an oblate spheroid: it has a slight but noticeable bulge around the equator. The outer atmosphere i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earth's Magnetic Field
Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from Earth's interior out into space, where it interacts with the solar wind, a stream of charged particles emanating from the Sun. The magnetic field is generated by electric currents due to the motion of convection currents of a mixture of molten iron and nickel in Earth's outer core: these convection currents are caused by heat escaping from the core, a natural process called a geodynamo. The magnitude of Earth's magnetic field at its surface ranges from . As an approximation, it is represented by a field of a magnetic dipole currently tilted at an angle of about 11° with respect to Earth's rotational axis, as if there were an enormous bar magnet placed at that angle through the center of Earth. The North geomagnetic pole actually represents the South pole of Earth's magnetic field, and conversely the South geomagnetic pole corresponds to the north pole of Earth's magneti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Milky Way
The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. The term ''Milky Way'' is a translation of the Latin ', from the Greek ('), meaning "milky circle". From Earth, the Milky Way appears as a band because its disk-shaped structure is viewed from within. Galileo Galilei first resolved the band of light into individual stars with his telescope in 1610. Until the early 1920s, most astronomers thought that the Milky Way contained all the stars in the Universe. Following the 1920 Great Debate between the astronomers Harlow Shapley and Heber Curtis, observations by Edwin Hubble showed that the Milky Way is just one of many galaxies. The Milky Way is a barred spiral galaxy with an estimated D25 isophotal diameter of , but only about 1,000 light years thick at the spiral arms (more at the bulge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecular Clouds
A molecular cloud, sometimes called a stellar nursery (if star formation is occurring within), is a type of interstellar cloud, the density and size of which permit absorption nebulae, the formation of molecules (most commonly molecular hydrogen, H2), and the formation of H II regions. This is in contrast to other areas of the interstellar medium that contain predominantly ionized gas. Molecular hydrogen is difficult to detect by infrared and radio observations, so the molecule most often used to determine the presence of H2 is carbon monoxide (CO). The ratio between CO luminosity and H2 mass is thought to be constant, although there are reasons to doubt this assumption in observations of some other galaxies. Within molecular clouds are regions with higher density, where much dust and many gas cores reside, called clumps. These clumps are the beginning of star formation if gravitational forces are sufficient to cause the dust and gas to collapse. History The form of molecular ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flux
Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications to physics. For transport phenomena, flux is a vector quantity, describing the magnitude and direction of the flow of a substance or property. In vector calculus flux is a scalar quantity, defined as the surface integral of the perpendicular component of a vector field over a surface. Terminology The word ''flux'' comes from Latin: ''fluxus'' means "flow", and ''fluere'' is "to flow". As '' fluxion'', this term was introduced into differential calculus by Isaac Newton. The concept of heat flux was a key contribution of Joseph Fourier, in the analysis of heat transfer phenomena. His seminal treatise ''Théorie analytique de la chaleur'' (''The Analytical Theory of Heat''), defines ''fluxion'' as a central quantity and proceeds to derive the now well-known e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weber (unit)
In physics, the weber ( ; symbol: Wb) is the unit of magnetic flux in the International System of Units (SI), whose units are volt-second. A magnetic flux density of one Wb/m2 (one weber per square metre) is one tesla. The weber is named after the German physicist Wilhelm Eduard Weber (1804–1891). Definition The weber may be defined in terms of Faraday's law, which relates a changing magnetic flux through a loop to the electric field around the loop. A change in flux of one weber per second will induce an electromotive force of one volt (produce an electric potential difference of one volt across two open-circuited terminals). Officially: That is: \mathrm = \mathrm\mathrm. One weber is also the total magnetix flux across a surface of one square meter perpendicular to a magnetic flux density of one tesla; that is, \mathrm = \mathrm\mathrm^2. Expressed only in SI base units, 1 tesla is: \mathrm = \dfrac. The weber is used in the definition of the henry as 1 weber per a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Area
Area is the quantity that expresses the extent of a region on the plane or on a curved surface. The area of a plane region or ''plane area'' refers to the area of a shape or planar lamina, while '' surface area'' refers to the area of an open surface or the boundary of a three-dimensional object. Area can be understood as the amount of material with a given thickness that would be necessary to fashion a model of the shape, or the amount of paint necessary to cover the surface with a single coat. It is the two-dimensional analogue of the length of a curve (a one-dimensional concept) or the volume of a solid (a three-dimensional concept). The area of a shape can be measured by comparing the shape to squares of a fixed size. In the International System of Units (SI), the standard unit of area is the square metre (written as m2), which is the area of a square whose sides are one metre long. A shape with an area of three square metres would have the same area as three such s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Integral
In mathematics, an integral assigns numbers to functions in a way that describes displacement, area, volume, and other concepts that arise by combining infinitesimal data. The process of finding integrals is called integration. Along with differentiation, integration is a fundamental, essential operation of calculus,Integral calculus is a very well established mathematical discipline for which there are many sources. See and , for example. and serves as a tool to solve problems in mathematics and physics involving the area of an arbitrary shape, the length of a curve, and the volume of a solid, among others. The integrals enumerated here are those termed definite integrals, which can be interpreted as the signed area of the region in the plane that is bounded by the graph of a given function between two points in the real line. Conventionally, areas above the horizontal axis of the plane are positive while areas below are negative. Integrals also refer to the concept ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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