Production

Production theory is one of the basic concepts of microeconomics; it is the study of production or the economic process of converting inputs into outputs. Producers seek to choose the combination of inputs and methods of combining them that will minimize cost in order to maximize their profits. The production uses resources to create a good …

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Consumer choice

The theory of consumer choice (or consumer demand theory) is the branch of microeconomics that relates preferences for the consumption of both goods and services to the consumption expenditures; ultimately, this relationship between preferences and consumption expenditures is used to relate preferences to consumer demand curves. Analogous to production theory, consumers will choose to purchase and consume a …

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Electrolyte

An electrolyte is a substance that produces an electrically conducting solution when dissolved in a polar solvent, such as water. The dissolved electrolyte separates into cations and anions, which disperse uniformly through the solvent. Electrically, such a solution is neutral. An electrolyte is what is called an ionic conductor. The electrolytes are capable of conducting electric current, …

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Molecule

A molecule is an electrically neutral group of two or more atoms held together by chemical bonds. A molecule is formed by a set of same atoms (in the case of the elements) or different from each other (in the case of the compounds). In the condensed state (solid and liquid) the molecules interact with each other …

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Bank

Banks facilitate using the money for transactions in the economy because people and firms can use bank accounts when selling or buying goods and services, when paying a worker or receiving payment, and when saving money or receiving a loan. In the financial capital market, banks are financial intermediaries; that is, they operate between savers who …

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Insurance

Insurance is a way of sharing risk. People in a group pay premiums for insurance against some unpleasant event, and those in the group who actually experience the unpleasant event then receive some compensation. The fundamental law of insurance is that what the average person pays in overtime cannot be less than what the average person …

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Enthalpy

If a chemical change is carried out at constant pressure and the only work done is caused by expansion or contraction, the change is called the enthalpy change with the symbol ΔH, or ΔH°298 for reactions occurring under standard state conditions. The value of ΔH for a reaction in one direction is equal in magnitude, but opposite in …

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Liquid crystal

Liquid crystals (LCs) are a state of matter which has properties between those of conventional liquids and those of solid crystals. The term liquid crystal is used to indicate the intermediate phases (mesophases) between that of crystalline solid and that of isotropic liquid of some substances. A substance can present several mesophases with a decreasing order …

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Standard conditions for temperature and pressure (STP)

Standard conditions for temperature and pressure (STP) are standard sets of conditions for experimental measurements to be established to allow comparisons to be made between different sets of data. STP should not be confused with the standard state of a material (pure substance, mixture, or solution) which is a reference point used to calculate its properties under different …

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Monomial

It is defined monomial as a literal algebraic expression, consisting of a numerical part (coefficient) and a literal part among which only multiplication and exponentiation operations appear; for example: \[\dfrac{1}{2}x;\;7x^2y;\;-9x^n\] The monomial degree is defined as the sum of all the exponents of the literal part. Monomes that have the same literal part (with identical exponent) are …

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Exponentiation

Exponentiation is one of the mathematical operations that replace multiple multiplications between equal numbers or variables, simplifying both writing and processing. If the exponent is greater than 1, the power is the product of as many factors as are indicated by the number of the exponent, all equal to the base. From this statement it is …

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Isometry

In mathematics, an isometry (from the Greek ἴσος, isos, which means equal | called also congruence, or congruent transformation) is a notion that generalizes that of rigid movement of an object or a geometric figure. Formally, it is a function between two metric spaces that preserves distances. An isometry is any geometric transformation defined in the plane or space …

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Inequation

The inequations, unlike the equations, are inequalities between monomials, or polynomials, for which we seek the solution of one or more literal variables, called unknowns (as for the equations). Some examples of inequations are: \(a<b\) \(x+y+z\leq 1\) \(n>1\) \(x\neq 0\) Intervals In mathematics, an interval is defined as the set of all the elements of an ordered set which are preceded …

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Binomial

Notable products between binomials Notable products are used in algebra for the literal calculation of the product between binomials. They are said to be notable because the product of some particular polynomials always reaches the same result. For this reason, it is possible to avoid, for these particular polynomials, the carrying out of all the calculation steps …

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Polynomial

Polynomial is defined as the algebraic sum of monomials. The monomials that make up a polynomial are called polynomial terms. For an expression to be a polynomial term, any variables in the expression must have whole-number powers (or else the “understood“ power of 1, as in \(x^1\), which is normally written as \(x\)).

Wimshurst machine

The Wimshurst influence machine is is a historic electrostatic generator, a machine for generating high voltages developed between 1880 and 1883 by British inventor James Wimshurst (1832-1903). The appearance is particular and is characterized by two vertically mounted discs that rotate in the opposite direction and two metal balls for discharging. It produces electrical discharges of a …

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Positron emission tomography (PET)

Positron emission tomography (PET) is a medical imaging technique involving the use of so-called radiopharmaceuticals, substances that emit radiation that is short-lived and therefore relatively safe to administer to the body. Although the first PET scanner was introduced in 1961, it took 15 more years before radiopharmaceuticals were combined with the technique and revolutionized its potential. …

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Unit operation

In chemical engineering and related fields, a unit operation is a basic step in a process; it consists of a single physical transformation that can take place inside a chemical apparatus of a chemical plant. Unit operations involve a physical change or chemical transformation such as separation, crystallization, evaporation, filtration, polymerization, isomerization, and other reactions.

Belt

The belt is a mechanical transmission element used to connect two shafts in a slightly elastic, but integral way, through the use of pulleys, whose center distance is rather high. The most common belts are distinguished, according to their shape, in flat, trapezoid (or trapezoidal) and toothed. The most widely used material is the rubberized fabric, synthetic …

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Ultrasonography

Ultrasonography is an imaging technique that uses the transmission of high-frequency sound waves into the body to generate an echo signal that is converted by a computer into a real-time image of anatomy and physiology. Ultrasonography is the least invasive of all imaging techniques, and it is therefore used more freely in sensitive situations such as …

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Actuator

An actuator is a mechanism by which an agent acts on an environment; furthermore, the agent can be either an artificial intelligent agent or any other autonomous being (human, animal). In a broad sense, an actuator is sometimes defined as any device that converts energy from one form to another so that it acts in …

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Transponder

A transponder is a component which, on receiving an ElectroMagnetic (EM) signal, often coded, will respond by sending a similar signal, usually after a known, controlled delay time. In telecommunications, the term transponder is a contraction of transmitter responder, sometimes abbreviated to XPDR, XPNDR, TPDR, has the following meanings: an automatic device that receives, amplifies, and retransmits …

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Compression strength

Compressive strength or compression strength is the capacity of a material or structure to withstand loads tending to reduce the size, as opposed to tensile strength, which withstands loads tending to elongate. In other words, compressive strength resists compression (being pushed together), whereas tensile strength resists tension (being pulled apart). In the study of the strength of materials, …

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Spectrometer

Spectrometers are devices for the precise measurement of energies or masses of the particles in a beam. These devices are used, for example, in the secondary beams to sort out the products of high-energy or nuclear reactions. Charged particles produced in these reactions are guided through a spectrometer to analyzing stations. Although no acceleration is performed …

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Semiconductor

Semiconductors, in the science and technology of materials, are materials, belonging to the category of semimetals, which can have a resistivity higher than that of conductors and lower than that of insulators; resistivity depends directly on temperature. The conductivity of semiconductors grows with temperature (i.e. the temperature coefficient of resistivity is negative) in the temperature …

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Ultimate tensile strength (UTS)

Ultimate tensile strength (UTS), often shortened to tensile strength (TS), ultimate strength, or Ftu within equations, is the capacity of a material or structure to withstand loads tending to elongate, as opposed to compressive strength, which withstands loads tending to reduce size. In other words, tensile strength resists tension (being pulled apart), whereas compressive strength resists compression (being pushed …

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Rigid body

A rigid body (also known as rigid object) is defined as an ideal (theoretical) material body such that the distances between assigned points of the same body remain always constant during motion. That is, each particle in a rigid body maintains defined the mutual distance with the other particles of the body itself, as well as being identified …

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Ductility

Ductility is a technological property of matter that indicates the ability of a body or material to deform plastically under load before breaking, which may be expressed as percent elongation or percent area reduction from a tensile test — for example, the ability to withstand plastic deformations. A body is much more ductile, the higher the …

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Laser

A laser optoelectronic device capable of emitting a coherent beam of light (a unidirectional, monochromatic radiation with a wavelength between infrared and ultraviolet) through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term “laser“ originated as an acronym for “light amplification by stimulated emission of radiation“. The first laser was built …

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Grashof number

The Grashof number is a dimensionless parameter which, unlike the Rayleigh number, contains information of a mechanical nature only. It contrasts the exclusive effects of viscosity with the floating force: \[Gr=\dfrac{F_g}{(F_v)^2}\] once the motion is triggered (Ra > 1708) to understand if the motion is laminar or turbulent (in natural convection) the Grashof number is evaluated; if …

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Capacitance

The electric capacitance is a scalar physical quantity that quantifies the aptitude of a conductive material to accumulate electric charge when it has an electric potential with respect to the environment or is subject to an electric potential difference with respect to other conducting bodies. Capacitance is the ratio of the change in an electric charge …

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Capacitor

A capacitor consists of two conducting plates separated by an insulating layer called a dielectric. Capacitors often differ in the size and arrangements of plates as well as the type of dielectric materials used. When a capacitor is connected in a circuit, the power source’s voltage forces electrons onto the surface of one plate and pulls electrons …

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Elastomer

Elastomer is defined as a macromolecular material (natural or synthetic polymer) that when subjected to high deformation (stretching with elongation even up to 5 or 10 times the initial length) within a certain temperature range, after the removal of the applied stress returns to the initial shape and size; this is possible thanks to their …

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Filter circuit

Circuits capable of selectively filtering one frequency or range of frequencies out of a mix of different frequencies in a circuit are called filter circuits, or filters. A common need for filter circuits is in high-performance stereo systems, where certain ranges of audio frequencies need to be amplified or suppressed for best sound quality and power efficiency. …

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Ampacity

The ampacity of a conductor, that is, the amount of current it can carry, is related to its electrical resistance: a lower-resistance conductor can carry a larger value of current. The ampacity of a conductor depends on its ability to dissipate heat without damage to the conductor or its insulation. This is a function of the insulation …

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Electric resistance

The electrical resistance is the opposition to the motion of the electrons through a conductor. It can be said that conductors have low resistance and insulators have very high resistance. This opposition to electric current depends on the type of material, its cross-sectional area, and its temperature. Resistance serves to limit the amount of current through the circuit …

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Magnetic resonance imaging (MRI)

Magnetic resonance imaging (MRI) is a noninvasive medical imaging technique based on a phenomenon of nuclear physics discovered in the 1930s, in which matter exposed to magnetic fields and radio waves was found to emit radio signals. In 1970, a physician and researcher named Raymond Damadian noticed that malignant (cancerous) tissue gave off different signals than …

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Mechanism

The term mechanism identifies an entity that has the constructive connotations, the mobility, the ability to transmit motion, force, energy, present in the definition of machine. The complex of several mechanisms connected together constitutes a machine. Mechanisms generally consist of moving components that can include: gears; belt and chain drives; cam and followers; linkage; friction devices, such …

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Voltage

The potential energy, stored in the form of an electric charge imbalance and capable of provoking electrons to flow through a conductor, can be expressed as a term called voltage (or electric potential difference, electric pressure, and electric tension), which technically is a measure of potential energy per unit charge of electrons or something a physicist would call …

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Pompilidae

Hymenoptera, Apocrita insect family; cosmopolitan. Pompilidae are commonly called spider wasps, spider-hunting wasps, or pompilid wasps. Up to 7 cm long, they have an enlarged head, large eyes, long antennae, an elongated abdomen, and reduced or missing wings; the females have a sting connected with poisonous glands, with which they paralyze spiders, on which they lay their eggs.

ABC protein

The ABC proteins constitute the largest family of proteins. They are present in all living species from Archaea to Homo sapiens. They make up to 4% of the full genome complement of bacteria such as Escherichia coli or Bacillus subtilis. Each eukaryote genome contains several dozens of members (over 100 in the plant Arabidopsis thaliana). …

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Pompiloidea

Pompiloidea is a superfamily that includes at least five families in the order Hymenoptera; cosmopolitan. Mutillidae (velvet ants) Myrmosidae (myrmosid wasps) Pompilidae (spider wasps) Sapygidae (sapygid wasps) Burmusculidae (extinct) Kingdom Animalia Phylum Arthropoda Subphylum Hexapoda Class Insecta Order Hymenoptera Superfamily Pompiloidea

Maya

The Maya were one Mesoamerican culture that had strong ties to Teotihuacan. Maya’s architectural and mathematical contributions were significant. Flourishing from roughly 2000 BCE to 900 CE in what is now Mexico, Belize, Honduras, and Guatemala, the Maya perfected the calendar and written language the Olmec had begun. They devised a written mathematical system to record crop …

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Steroid

Unlike the phospholipids and fats, steroids have a fused ring structure. Although they do not resemble the other lipids, scientists group them with them because they are also hydrophobic and insoluble in water. All steroids have four linked carbon rings and several of them, like cholesterol, have a short tail. Many steroids also have the –OH functional …

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Nectar

Nectar is a sugar-rich liquid produced by plants in glands called nectaries or nectarines, either within the flowers with which it attracts pollinating animals, or by extrafloral nectaries, which provide a nutrient source to animal mutualists, which in turn provide antiherbivore protection. Nectar is primarily an aqueous solution of sugars (fructose, glucose, and sucrose), but …

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Larva

A larva (plural larvae) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. In addition to the anatomo-physiological characteristics, the larvae often have different habitats, locomotion, and dietary regimen from the adult, so that they occupy …

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Cellulose

Cellulose is the most abundant natural biopolymer. Cellulose mostly comprises a plant’s cell wall. This provides the cell structural support. Wood and paper are mostly cellulosic in nature.In cellulose, glucose monomers are linked in unbranched chains by β 1-4 glycosidic linkages. Because of the way the glucose subunits are joined, every glucose monomer is flipped relative to the …

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Phospholipid

A phospholipid is an amphipathic molecule, meaning it has a hydrophobic and a hydrophilic part. Phospholipids are major plasma membrane constituents that comprise cells’ outermost layer. Like fats, they are comprised of fatty acid chains attached to a glycerol or sphingosine backbone. However, instead of three fatty acids attached as in triglycerides, there are two fatty acids forming …

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Bacteria

Bacteria (singular bacterium) are a type of biological cell. Each bacterium is a single cell. They constitute a large domain of prokaryotic microorganisms. The cell structure is simpler than that of other organisms as there is no nucleus or membrane-bound organelles. Instead, their control center containing the genetic information is contained in a single loop of DNA. …

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Amino acid

Amino acids are the monomers that comprise proteins. Each amino acid has the same fundamental structure, which consists of a central carbon atom, or the alpha (\(\alpha\)) carbon, bonded to an amino group (NH2), a carboxyl group (COOH), and to a hydrogen atom. Every amino acid also has another atom or group of atoms bonded to …

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Trilobite

Trilobites are a group of formerly numerous marine animals that disappeared in the Permian–Triassic extinction event, though they were in decline prior to this killing blow, having been reduced to one order in the Late Devonian extinction.

Chelicerata

Chelicerates include horseshoe crabs, spiders, mites, scorpions and related organisms. They are characterised by the presence of chelicerae, appendages just above / in front of the mouth. Chelicerae appear in scorpions and horseshoe crabs as tiny claws that they use in feeding, but those of spiders have developed as fangs that inject venom.

Myriapoda

Myriapoda (from Ancient Greek μυρίος (muríos) ‘ten thousand’, and πούς (poús) ‘foot’) is a subphylum of arthropods containing millipedes, centipedes, and their relatives; have many body segments, each segment bearing one or two pairs of legs (or in a few cases being legless). They are sometimes grouped with the hexapods. Myriapods have in common a body …

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Crustacean

Crustaceans (Crustacea Brünnich, 1772) constitute a subphylum of the Arthropods that includes primarily marine aquatic animals, although they are also widely found in fresh waters and a few terrestrial species are known. Thanks to various molecular studies, it is now well accepted that the crustacean group is paraphyletic and includes all animals in the clade …

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Hexapoda

The subphylum Hexapoda (from Greek for ‘six legs’) is the largest (in terms of number of species) grouping of arthropods and includes two classes: the Insecta (Ectognatha) and the Entognatha. This last class groups three small orders of wingless hexapods: Collembola, Protura, and Diplura. Hexapods comprise insects and three small orders of insect-like animals with six …

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Biogeography

Biogeography is the science that studies the distribution in space and time of living organisms and the causes that determine it. In fact, organisms and biological communities often vary on a regular basis following geographical gradients such as latitude, altitude, isolation and habitat. This science deals with investigating the extension, development, rotation over time, and overlapping …

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Biologist

Biologists may study anything from the microscopic or submicroscopic view of a cell to ecosystems and the whole living planet. The term “biologist“ is used to group scientists specialized mainly in three areas: Botany, which studies plants; Zoology, which studies the animal kingdom; and Microbiology, which studies microbes and unicellular organisms. Some other subcategories of Biology …

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Bacillus

Bacillus species are rod-shaped, endospore-forming aerobic or facultatively anaerobic, Gram-positive bacteria; in some species cultures may turn Gram-negative with age. The many species of the genus exhibit a wide range of physiologic abilities that allow them to live in every natural environment. Only one endospore is formed per cell. The spores are resistant to heat, cold, …

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Anthrax

Anthrax is caused by Bacillus anthracis. Humans acquire the disease directly from contact with infected herbivores or indirectly via their products. The clinical forms include: cutaneous anthrax (eschar with edema), from handling infected material (this accounts for more than 95 percent of cases); intestinal anthrax, from eating infected meat; pulmonary anthrax, from inhaling spore-laden dust. Several other Bacillus spp, in …

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Bacteriology

Bacteriology (from the Greek βακτήριον “bacterium” e λόγος “study”) is the branch of biology that studies morphology, ecology, genetics, and biochemistry of bacteria as well as many other aspects related to them (medicine, industry, and agriculture). Bacteria were discovered in 1676 by Anton von Leeuwenhoek. Modern techniques of study originate from about 1870 with the use …

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Bacteriophage

A bacteriophage (derived from “bacteria“ and the Greek φαγεῖν (phagein), meaning “to devour,“ informally known as a phage) is a virus that infects and replicates within bacteria and archaea. The infection may or may not lead to the death of the bacterium, depending on the phage and sometimes on conditions. Each bacteriophage is specific to one form of the bacterium. Bacteriophages make up …

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Ultramicrobacteria (dwarf bacteria)

Ultramicrobacteria (also known as dwarf bacteria) are bacteria that are smaller than 0.1 μm3 under all growth conditions. They have shrunk to less than a thousandth of their normal volume because they have used up virtually all their internal reserves. These emaciated microbes are commonly found at great depths under the Earth’s surface (see endoliths) where nutrients are scarce. In …

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Endolith

An endolith is an organism (archaeon, bacterium, fungus, lichen, alga, or amoeba) that lives inside rocks, corals, animal shells, or in the pores between mineral grains of a rock. Endoliths have been found inhabiting the Earth’s crust at depths up to nearly 3 kilometers. The extreme depth at which endoliths can exist has yet to be established. …

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Focus

In geometrical optics, is called focus (or image point) the point in the construction of a conic section where light rays originating from a point on the object converge. The word comes from the Latin for hearth or fireplace and appears to have been first used in mathematics, in describing an ellipse, by Johannes Kepler. Aberrations of …

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Pyroelectricity (pyroelectric effect)

Pyroelectricity is a property of certain materials (especially crystals which are naturally electrically polarized) to generate a temporary voltage when they are heated or cooled. The change in temperature modifies the positions of the atoms slightly within the crystal structure, such that the polarization of the material changes. This polarization change gives rise to a voltage …

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Triboelectric effect

The triboelectric effect (also known as triboelectric charging) is a type of contact electrification in which certain materials become electrically charged after they come into frictional contact with a different material, and are then separated. The polarity and strength of the charges produced differ according to the materials, surface roughness, temperature, strain, and other properties. It is …

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Rheid

In geology, a rheid is a substance whose temperature is below the melting point and whose deformation by viscous flow during the time of observation is at least three orders of magnitude \((10^3)\) greater than the elastic deformation under the given conditions. A material is a rheid by virtue of the time of observation. The term, coined …

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Buoyancy

Buoyancy or upthrust is an upward force exerted by a fluid that opposes the weight of an immersed object; it is what makes an object float, sink, or remain neutrally buoyant in the water (or other fluids). The symbol for the magnitude of buoyancy is \(B\) or \(F_B\). As a vector, it must be stated with both magnitude …

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Candela

The candela (cd) is the base unit of luminous intensity in the International System of Units (SI); that is, luminous power per unit solid angle emitted by a point light source in a particular direction. The units of luminous intensity based on flame or incandescent filament standards in use in various countries before 1948 were replaced initially …

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Work

In general, work is defined as a productive activity, which implies the implementation of rigorous and methodical, intellectual and/or manual knowledge, to produce and distribute goods and services in exchange for compensation, monetary or otherwise, an important topic of study for both social sciences (sociology, politics, law, economics) that the abstract and natural sciences (physics and geography). …

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Velocity

The average speed of an object is defined as the distance traveled divided by the time elapsed. The velocity of an object is the rate of change of its position with respect to a frame of reference, and is a function of time. Velocity is a vector quantity, and average velocity can be defined as …

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Speed

The speed, according to its technical definition in kinematics, is a scalar quantity that indicates the rate of motion distance per time and represents the magnitude of the change in position of an object. Its units are length and time. \[v=\dfrac{d}{t}\] where \(v\) is speed (also called average speed), \(d\) is distance, and \(t\) is time. …

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Biot–Savart law

Biot-Savart’s law, named after the French physicists Jean-Baptiste Biot and Félix Savart, can refer to two different laws of magnetostatics that allow to calculate the magnetic field generated by electric currents. The more general one, empirically verified, is also called Laplace’s first formula, from the name of the French physicist, mathematician and astronomer Pierre-Simon Laplace; …

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