1.
Electrical resistance
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The electrical resistance of an electrical conductor is a measure of the difficulty to pass an electric current through that conductor. The inverse quantity is electrical conductance, and is the ease with which a current passes. Electrical resistance shares some parallels with the notion of mechanical friction. The SI unit of resistance is the ohm, while electrical conductance is measured in siemens. An object of uniform cross section has a proportional to its resistivity and length. All materials show some resistance, except for superconductors, which have a resistance of zero and this proportionality is called Ohms law, and materials that satisfy it are called ohmic materials. In other cases, such as a diode or battery, V and I are not directly proportional. The ratio V/I is sometimes useful, and is referred to as a chordal resistance or static resistance, since it corresponds to the inverse slope of a chord between the origin and an I–V curve. In other situations, the derivative d V d I may be most useful, in the hydraulic analogy, current flowing through a wire is like water flowing through a pipe, and the voltage drop across the wire is like the pressure drop that pushes water through the pipe. Conductance is proportional to how much flow occurs for a given pressure, the voltage drop, not the voltage itself, provides the driving force pushing current through a resistor. In hydraulics, it is similar, The pressure difference between two sides of a pipe, not the pressure itself, determines the flow through it, for example, there may be a large water pressure above the pipe, which tries to push water down through the pipe. But there may be a large water pressure below the pipe. If these pressures are equal, no water flows, in the same way, a long, thin copper wire has higher resistance than a short, thick copper wire. A pipe filled with hair restricts the flow of more than a clean pipe of the same shape. The difference between copper, steel, and rubber is related to their structure and electron configuration. In addition to geometry and material, there are other factors that influence resistance and conductance, such as temperature. Substances in which electricity can flow are called conductors, a piece of conducting material of a particular resistance meant for use in a circuit is called a resistor. Conductors are made of high-conductivity materials such as metals, in particular copper, Resistors, on the other hand, are made of a wide variety of materials depending on factors such as the desired resistance, amount of energy that it needs to dissipate, precision, and costs

2.
Superconductor
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It was discovered by Dutch physicist Heike Kamerlingh Onnes on April 8,1911, in Leiden. Like ferromagnetism and atomic spectral lines, superconductivity is a mechanical phenomenon. It is characterized by the Meissner effect, the ejection of magnetic field lines from the interior of the superconductor as it transitions into the superconducting state. The occurrence of the Meissner effect indicates that superconductivity cannot be simply as the idealization of perfect conductivity in classical physics. The electrical resistance of a metallic conductor decreases gradually as temperature is lowered, in ordinary conductors, such as copper or silver, this decrease is limited by impurities and other defects. Even near absolute zero, a sample of a normal conductor shows some resistance. In a superconductor, the resistance drops abruptly to zero when the material is cooled below its critical temperature, an electric current flowing through a loop of superconducting wire can persist indefinitely with no power source. In 1986, it was discovered that some cuprate-perovskite ceramic materials have a temperature above 90 K. Such a high temperature is theoretically impossible for a conventional superconductor. There are many criteria by which superconductors are classified, by theory of operation, It is conventional if it can be explained by the BCS theory or its derivatives, or unconventional, otherwise. By material, Superconductor material classes include chemical elements, alloys, ceramics, on the other hand, there is a class of properties that are independent of the underlying material. For instance, all superconductors have exactly zero resistivity to low applied currents when there is no magnetic field present or if the field does not exceed a critical value. The resistance of the sample is given by Ohms law as R = V / I, if the voltage is zero, this means that the resistance is zero. Superconductors are also able to maintain a current with no applied voltage whatsoever, experiments have demonstrated that currents in superconducting coils can persist for years without any measurable degradation. Experimental evidence points to a current lifetime of at least 100,000 years, theoretical estimates for the lifetime of a persistent current can exceed the estimated lifetime of the universe, depending on the wire geometry and the temperature. In a normal conductor, an electric current may be visualized as a fluid of electrons moving across an ionic lattice. As a result, the energy carried by the current is constantly being dissipated and this is the phenomenon of electrical resistance and Joule heating. The situation is different in a superconductor, in a conventional superconductor, the electronic fluid cannot be resolved into individual electrons

3.
Silver
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Silver is a metallic element with symbol Ag and atomic number 47. The symbol Ag stems from Latin argentum, derived from the Greek ὰργὀς, a soft, white, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. The metal is found in the Earths crust in the pure, free form, as an alloy with gold and other metals. Most silver is produced as a byproduct of copper, gold, lead, Silver is more abundant than gold, but it is much less abundant as a native metal. Its purity is measured on a per mille basis, a 94%-pure alloy is described as 0.940 fine. As one of the seven metals of antiquity, silver has had a role in most human cultures. Silver has long valued as a precious metal. Silver metal is used in many premodern monetary systems in bullion coins, Silver is used in numerous applications other than currency, such as solar panels, water filtration, jewelry, ornaments, high-value tableware and utensils, and as an investment medium. Silver is used industrially in electrical contacts and conductors, in specialized mirrors, window coatings, Silver compounds are used in photographic film and X-rays. Dilute silver nitrate solutions and other compounds are used as disinfectants and microbiocides, added to bandages and wound-dressings, catheters. Silver is similar in its physical and chemical properties to its two neighbours in group 11 of the periodic table, copper and gold. This distinctive electron configuration, with an electron in the highest occupied s subshell over a filled d subshell. Silver is a soft, ductile and malleable transition metal. Silver crystallizes in a cubic lattice with bulk coordination number 12. Unlike metals with incomplete d-shells, metallic bonds in silver are lacking a covalent character and are relatively weak and this observation explains the low hardness and high ductility of single crystals of silver. Silver has a brilliant white metallic luster that can take a polish. Protected silver has greater optical reflectivity than aluminium at all wavelengths longer than ~450 nm, at wavelengths shorter than 450 nm, silvers reflectivity is inferior to that of aluminium and drops to zero near 310 nm. The electrical conductivity of silver is the greatest of all metals, greater even than copper, during World War II in the US,13540 tons of silver were used in electromagnets for enriching uranium, mainly because of the wartime shortage of copper

4.
Zero-ohm link
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A zero-ohm link or zero-ohm resistor is a wire link used to connect traces on a printed circuit board that is packaged in the same physical package format as a resistor. This format allows it to be placed on the board using the same automated equipment used to place other resistors. Zero-ohm resistors may be packaged like cylindrical resistors, or like surface-mount resistors, the resistance is only approximately zero, only a maximum is specified. A percentage tolerance would not make sense, as it would be specified as a percentage of the value of zero ohms. An axial-lead through-hole zero-ohm resistor is generally marked with a black band. Surface-mount resistors are marked with a single 0 or 000. The low-ohm resistors are easily obtained with 5% or 1% tolerances on a maximum specified resistance, for example, a surface-mounted 0805 size resistor of 0.003 ohms, rated at 1/2 watt can, in theory, safely pass up to 12.9 amperes of current. In practice, when approaching the limit for a given package. The cost associated with taking up more space for the larger package may also be a consideration. In this example, for 12 amperes to pass through the jumper, in contrast, a worst-case zero-ohm real-world jumper with 0. 05-ohm impedance in a similar 0805 package could only pass 3.1 amperes maximum. The use of specific tolerance resistances is a safer design practice for higher currents than the zero-ohm option

5.
Electronic color code
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The electronic color code is used to indicate the values or ratings of electronic components, usually for resistors, but also for capacitors, inductors, diodes and others. A separate code, the 25-pair color code, is used to identify wires in some telecommunications cables, in 1952, it was standardized in IEC62,1952 by the International Electrotechnical Commission and since 1963 also published as EIA RS-279. Originally only meant to be used for fixed resistors, the code was extended to also cover capacitors with IEC62,1968. The code was adopted by national standards like DIN40825, BS1852. The current international standard defining marking codes for resistors and capacitors is IEC60062,2016, colorbands were used because they were easily and cheaply printed on tiny components. However, there were drawbacks, especially for color blind people, overheating of a component or dirt accumulation, may make it impossible to distinguish brown from red or orange. Advances in printing technology have now made printed numbers practical on small components, where passive components come in surface mount packages, their values are identified with printed alphanumeric codes instead of a color code. To distinguish left from there is a gap between the C and D bands. Band A is the first significant figure of component value band B is the significant figure. Gold signifies that the tolerance is ±5%, so the resistance could lie anywhere between 4,465 and 4,935 ohms. Resistors manufactured for use may also include a fifth band which indicates component failure rate. Tight tolerance resistors may have three bands for significant figures rather than two, or an additional band indicating temperature coefficient, in units of ppm/K, all coded components have at least two value bands and a multiplier, other bands are optional. The standard color code per IEC60062,2016 is as follows, Resistors use preferred numbers for their specific values and these values repeat for every decade of magnitude,6.8,68,680, and so forth. In the E24 series the values are related by the 24th root of 10, while E12 series are related by the 12th root of 10, the tolerance of device values is arranged so that every value corresponds to a preferred number, within the required tolerance. Zero ohm resistors are made as lengths of wire wrapped in a body which can be substituted for another resistor value in automatic insertion equipment. They are marked with a black band. The other end of the resistor was colored gold or silver to give the tolerance, capacitors may be marked with 4 or more colored bands or dots. The colors encode the first and second most significant digits of the value, additional bands have meanings which may vary from one type to another

6.
Energy density
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Energy density is the amount of energy stored in a given system or region of space per unit volume. Colloquially it may also be used for energy per unit mass, often only the useful or extractable energy is measured, which is to say that chemically inaccessible energy such as rest mass energy is ignored. In short, pressure is a measure of the enthalpy per unit volume of a system, a pressure gradient has a potential to perform work on the surroundings by converting enthalpy until equilibrium is reached. There are many different types of stored in materials. In order of the magnitude of the energy released, these types of reactions are, nuclear, chemical, electrochemical. Chemical reactions are used by animals to derive energy from food, electrochemical reactions are used by most mobile devices such as laptop computers and mobile phones to release the energy from batteries. The following is a list of the energy densities of commonly used or well-known energy storage materials. Note that this list does not consider the mass of reactants commonly available such as the oxygen required for combustion or the efficiency in use. The following unit conversions may be helpful when considering the data in the table,1 MJ ≈0.28 kWh ≈0.37 HPh. In energy storage applications the energy density relates the mass of a store to the volume of the storage facility. The higher the density of the fuel, the more energy may be stored or transported for the same amount of volume. The energy density of a fuel per unit mass is called the energy of that fuel. The greatest energy source by far is mass itself and this energy, E = mc2, where m = ρV, ρ is the mass per unit volume, V is the volume of the mass itself and c is the speed of light. This energy, however, can be released only by the processes of nuclear fission, nuclear fusion, nuclear reactions cannot be realized by chemical reactions such as combustion. Although greater matter densities can be achieved, the density of a star would approximate the most dense system capable of matter-antimatter annihilation possible. A black hole, although denser than a star, does not have an equivalent anti-particle form. In the case of small black holes the power output would be tremendous. The highest density sources of energy aside from antimatter are fusion and fission, fusion includes energy from the sun which will be available for billions of years but so far, sustained fusion power production continues to be elusive

7.
Orders of magnitude (mass)
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To help compare different orders of magnitude, the following lists describe various mass levels between 10−40 kg and 1053 kg. The table below is based on the kilogram, the unit of mass in the International System of Units. The kilogram is the standard unit to include an SI prefix as part of its name. The gram is an SI derived unit of mass, however, the names of all SI mass units are based on gram, rather than on kilogram, thus 103 kg is a megagram, not a kilokilogram. The tonne is a SI-compatible unit of equal to a megagram. The unit is in use for masses above about 103 kg and is often used with SI prefixes. Other units of mass are also in use, historical units include the stone, the pound, the carat, and the grain. For subatomic particles, physicists use the equivalent to the energy represented by an electronvolt. At the atomic level, chemists use the mass of one-twelfth of a carbon-12 atom, astronomers use the mass of the sun. Unlike other physical quantities, mass-energy does not have an a priori expected minimal quantity, as is the case with time or length, plancks law allows for the existence of photons with arbitrarily low energies. This series on orders of magnitude does not have a range of larger masses Mass units conversion calculator Mass units conversion calculator JavaScript

8.
Orders of magnitude (numbers)
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This list contains selected positive numbers in increasing order, including counts of things, dimensionless quantity and probabilities. Mathematics – Writing, Approximately 10−183,800 is a rough first estimate of the probability that a monkey, however, taking punctuation, capitalization, and spacing into account, the actual probability is far lower, around 10−360,783. Computing, The number 1×10−6176 is equal to the smallest positive non-zero value that can be represented by a quadruple-precision IEEE decimal floating-point value, Computing, The number 6. 5×10−4966 is approximately equal to the smallest positive non-zero value that can be represented by a quadruple-precision IEEE floating-point value. Computing, The number 3. 6×10−4951 is approximately equal to the smallest positive non-zero value that can be represented by a 80-bit x86 double-extended IEEE floating-point value. Computing, The number 1×10−398 is equal to the smallest positive non-zero value that can be represented by a double-precision IEEE decimal floating-point value, Computing, The number 4. 9×10−324 is approximately equal to the smallest positive non-zero value that can be represented by a double-precision IEEE floating-point value. Computing, The number 1×10−101 is equal to the smallest positive non-zero value that can be represented by a single-precision IEEE decimal floating-point value, Mathematics, The probability in a game of bridge of all four players getting a complete suit is approximately 4. 47×10−28. ISO, yocto- ISO, zepto- Mathematics, The probability of matching 20 numbers for 20 in a game of keno is approximately 2.83 × 10−19. ISO, atto- Mathematics, The probability of rolling snake eyes 10 times in a row on a pair of dice is about 2. 74×10−16. ISO, micro- Mathematics – Poker, The odds of being dealt a flush in poker are 649,739 to 1 against. Mathematics – Poker, The odds of being dealt a flush in poker are 72,192 to 1 against. Mathematics – Poker, The odds of being dealt a four of a kind in poker are 4,164 to 1 against, for a probability of 2.4 × 10−4. ISO, milli- Mathematics – Poker, The odds of being dealt a full house in poker are 693 to 1 against, for a probability of 1.4 × 10−3. Mathematics – Poker, The odds of being dealt a flush in poker are 507.8 to 1 against, Mathematics – Poker, The odds of being dealt a straight in poker are 253.8 to 1 against, for a probability of 4 × 10−3. Physics, α =0.007297352570, the fine-structure constant, ISO, deci- Mathematics – Poker, The odds of being dealt only one pair in poker are about 5 to 2 against, for a probability of 0.42. Demography, The population of Monowi, a village in Nebraska. Mathematics, √2 ≈1.414213562373095489, the ratio of the diagonal of a square to its side length. Mathematics, φ ≈1.618033988749895848, the golden ratio Mathematics, the number system understood by most computers, human scale, There are 10 digits on a pair of human hands, and 10 toes on a pair of human feet. Mathematics, The number system used in life, the decimal system, has 10 digits,0,1,2,3,4,5,6,7,8,9

9.
Orders of magnitude (power)
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This page lists examples of the power in watts produced by various sources of energy. They are grouped by orders of magnitude, and each section covers three orders of magnitude, or a factor of one thousand,1.64 × 10−27 watt – phys, approximate power of gravitational radiation emitted by a 1000 kg satellite in geosynchronous orbit around the Earth. ~10 zW – tech, approximate power of Galileo space probes radio signal as received on earth by a 70-meter DSN antenna,1 aW – phys, approximate power scale at which operation of nanoelectromechanical systems are overwhelmed by thermal fluctuations. 100 aW – tech, the GPS signal strength measured at the surface of the Earth, for reference, about 10,000 100-watt lightbulbs or 5,000 computer systems would be needed to draw 1 MW. Also,1 MW is approximately 1360 horsepower, modern high-power diesel-electric locomotives typically have a peak power of 3–5 MW, while a typical modern nuclear power plant produces on the order of 500–2000 MW peak output. 8.21 GW – tech, capacity of the Kashiwazaki-Kariwa Nuclear Power Plant,73.1 GW - tech, total installed power capacity of Turkey on December 31,2015. 101.6 GW – tech, peak power consumption of France 166 GW – tech. 433 GW – tech, total installed wind turbine capacity at end of 2015,700 GW – biomed, humankind basal metabolic rate as of 2013. 2 TW – astro, approximate power generated between the surfaces of Jupiter and its moon Io due to Jupiters tremendous magnetic field,3.34 TW – geo, average total power consumption of the US in 200518. 1.1 PW – tech, worlds most powerful laser pulses by laser still in operation, ~2 X1.00 PW – tech, Omega EP laser power at the Laboratory for Laser Energetics. There are two beams that are combined. 1.25 PW – tech, worlds most powerful laser pulses,1.4 PW – geo, estimated heat flux transported by the Gulf Stream. 4 PW – geo, estimated heat flux transported by Earths atmosphere. 5.13 PW – tech, worlds most powerful laser pulses, 10–100 PW geo, estimated total power output of a Type-I civilization on the Kardashev scale. Barty also gave a talk on Laser-Based Nuclear Photonics at the SPIE meeting. 135 ZW – astro, approximate luminosity of Wolf 359 10-100 YW – geo, estimated total power output of a Type-II civilization on the Kardashev scale

10.
Orders of magnitude (radiation)
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Recognized effects of higher acute radiation doses are described in more detail in the article on radiation poisoning.01 mSv. Light radiation sickness begins at about 50–100 rad, the following table includes some dosages for comparison purposes, using millisieverts. Thus 100 mSv is considered twice in the table below – once as received over a 5-year period, the table describes doses and their official limits, rather than effects. Dose can be decreased down to 3 Gy through the use of a 10 gram/cm² alumunium shield

11.
Sound pressure
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Sound pressure or acoustic pressure is the local pressure deviation from the ambient atmospheric pressure, caused by a sound wave. In air, sound pressure can be measured using a microphone, the SI unit of sound pressure is the pascal. A sound wave in a medium causes a deviation in the local ambient pressure. Sound pressure, denoted p, is defined by p t o t a l = p s t a t + p, in a sound wave, the complementary variable to sound pressure is the particle velocity. Together they determine the intensity of the wave. Sound intensity, denoted I and measured in W·m−2 in SI units, is defined by I = p v. Consequently, the amplitude of the displacement is related to that of the acoustic velocity. This relationship is an inverse-proportional law, if the sound pressure p1 is measured at a distance r1 from the centre of the sphere, the sound pressure p2 at another position r2 can be calculated, p 2 = r 1 r 2 p 1. The inverse-proportional law for sound pressure comes from the law for sound intensity. Indeed, I = p v = p ∝ p 2, the sound pressure may vary in direction from the centre of the sphere as well, so measurements at different angles may be necessary, depending on the situation. An obvious example of a sound source whose spherical sound wave varies in level in different directions is a bullhorn, Sound pressure level or acoustic pressure level is a logarithmic measure of the effective pressure of a sound relative to a reference value. The commonly used reference sound pressure in air is p 0 =20 μ P a, which is often considered as the threshold of human hearing. The proper notations for sound pressure level using this reference are Lp/ or Lp, most sound level measurements will be made relative to this reference, meaning 1 Pa will equal an SPL of 94 dB. In other media, such as underwater, a level of 1 μPa is used. These references are defined in ANSI S1. 1-1994, the lower limit of audibility is defined as SPL of 0 dB, but the upper limit is not as clearly defined. Ears detect changes in sound pressure, human hearing does not have a flat spectral sensitivity relative to frequency versus amplitude. Humans do not perceive low- and high-frequency sounds as well as they perceive sounds between 3,000 and 4,000 Hz, as shown in the equal-loudness contour. Because the frequency response of human hearing changes with amplitude, three weightings have been established for measuring pressure, A, B and C. A-weighting applies to sound pressures levels up to 55 dB, B-weighting applies to sound levels between 55 dB and 85 dB, and C-weighting is for measuring sound pressure levels above 85 dB