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As the electrical resistance of most metals is dependent upon the temperature of the metal ( tungsten is a popular choice for hot-wires ), a relationship can be obtained between the resistance of the wire and the flow speed.
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electrical and resistance
Some common examples are the high electrical conductivity of pure copper, the excellent deep drawing qualities of cartridge case brass, the low-friction properties of bearing bronze, the resonant qualities of bell bronze, and the resistance to corrosion by sea water of several bronze alloys.
The behavior of the horizon in this situation is a dissipative system that is closely analogous to that of a conductive stretchy membrane with friction and electrical resistance — the membrane paradigm.
Superconductivity is a phenomenon of exactly zero electrical resistance and expulsion of magnetic fields occurring in certain materials when cooled below a characteristic critical temperature.
* Heating element, a device that generates heat by electrical resistance
* Equivalent series resistance, the resistive parts of the impedance of certain electrical components
Presence of alkaline metal ions has also detrimental effect to the loss tangent of the glass, and to its electrical resistance ; glasses for electronics ( sealing, vacuum tubes, lamps ...) have to take this in account.
The high ionic radius of the Pb < sup > 2 +</ sup > ion renders it highly immobile in the matrix and hinders the movement of other ions ; lead glasses therefore have high electrical resistance, about two orders of magnitude higher than soda-lime glass ( 10 < sup > 8. 5 </ sup > vs 10 < sup > 6. 5 </ sup > Ohm · cm, DC at 250 ° C ).
Similarly, if one connects two electrical resistors in parallel, one having resistance x ( e. g. 60Ω ) and one having resistance y ( e. g. 40Ω ), then the effect is the same as if one had used two resistors with the same resistance, both equal to the harmonic mean of x and y ( 48Ω ): the equivalent resistance in either case is 24Ω ( one-half of the harmonic mean ).
An ideal inductor would offer no resistance to a constant direct current ; however, only superconducting inductors have truly zero electrical resistance.
The Q factor of an inductor can be found through the following formula, where R is its internal ( Series Model ) electrical resistance and is the inductive reactance at resonance:
BCS theory explains conventional superconductivity, the ability of certain metals at low temperatures to conduct electricity without electrical resistance.
It has a few characteristic properties: high density, softness, ductility and malleability, poor electrical conductivity compared to other metals, high resistance to corrosion, and ability to react with organic chemicals.
" Myelin decreases capacitance across the cell membrane, and increases electrical resistance.
This means there are dissipative processes such as friction or electrical resistance which continually convert some of the energy stored in the oscillator into heat in the environment.
** For ohm – SI unit of electrical resistance ; formerly also used upside down () to represent mho, the old name for the inverse of an ohm ( now siemens with symbol S ) used for electrical conductance.
File: Georg Simon Ohm3. jpg | Georg Ohm ( 1789-1854 ): found that there is a direct proportionality between the electric current I and the potential difference ( voltage ) V applied across a conductor, and that this current is inversely proportional to the resistance R in the circuit, or I = V / R, known as Ohm's law, namesake of the unit of electrical resistance ( the ohm )
Unlike general-purpose computers, the PLC is designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact.
electrical and most
The sea of electrons in metallic bonds causes the characteristically good electrical and thermal conductivity of metals, and also their " shiny " reflection of most frequencies of white light.
In metals, which make up the wires and other conductors in most electrical circuits, the positive charges are immobile, and the charge carriers are electrons.
A semiconductor diode, the most common type today, is a crystalline piece of semiconductor material with a p-n junction connected to two electrical terminals.
Initially such topics cover most, if not all, of the sub-disciplines of electrical engineering.
Outside of Europe and North America, engineering graduates per-capita, and hence probably electrical engineering graduates also, are most numerous in Taiwan, Japan, and South Korea.
Today most engineering work involves the use of computers and it is commonplace to use computer-aided design programs when designing electrical systems.
Although most electrical engineers will understand basic circuit theory ( that is the interactions of elements such as resistors, capacitors, diodes, transistors and inductors in a circuit ), the theories employed by engineers generally depend upon the work they do.
Perhaps the most important technical skills for electrical engineers are reflected in university programs, which emphasize strong numerical skills, computer literacy and the ability to understand the technical language and concepts that relate to electrical engineering.
Oil was 5. 5 %, as it is the most expensive common commodity used to produce electrical energy.
In most cases, the cables are just changed from electrical to optical fiber cables.
The most common conversion factor, especially for electrical power, is 1 hp = 746 watts.
In most lasers this medium consists of population of atoms which have been excited into such a state by means of an outside light source, or an electrical field which supplies energy for atoms to absorb and be transformed into their excited states.
Copper alloys have been known since prehistory — bronze gave the Bronze Age its name — and have many applications today, most importantly in electrical wiring.
Chemically, the precious metals are less reactive than most elements, have high luster and high electrical conductivity.
Home electrical systems, for the most part, are wired with copper wire for its good conducting properties.
* 1891 – The International Electro-Technical Exhibition opens in Frankfurt, Germany, and will feature the world's first long distance transmission of high-power, three-phase electrical current ( the most common form today ).
A CPU socket provides many functions, including a physical structure to support the CPU, support for a heat sink, facilitating replacement ( as well as reducing cost ), and most importantly, forming an electrical interface both with the CPU and the PCB.
Neurons can be distinguished from other cells in a number of ways, but their most fundamental property is that they communicate with other cells via synapses, which are membrane-to-membrane junctions containing molecular machinery that allows rapid transmission of signals, either electrical or chemical.
Nighttime wind power is considered the most economical form of electrical power with which to synthesize fuel, because the load curve for electricity peaks sharply during the warmest hours of the day, but wind tends to blow slightly more at night than during the day.
Radar signals are reflected especially well by materials of considerable electrical conductivity — especially by most metals, by seawater, by wet land, and by wetlands.
While chemical synapses are found between both excitatory and inhibitory neurons, electrical synapses are most commonly found between smaller local inhibitory neurons.
The most familiar form of switch is a manually operated electromechanical device with one or more sets of electrical contacts, which are connected to external circuits.
Condensing turbines are most commonly found in electrical power plants.
electrical and metals
The first theoretical description of metals was given by Paul Drude in 1900 with the Drude model, which explained electrical and thermal properties by describing a metal as an ideal gas of then-newly discovered electrons.
In 1821, Estonian-German physicist Thomas Johann Seebeck demonstrated the electrical potential in the juncture points of two dissimilar metals when there is a heat difference between the joints.
In installations where copper pipe has been fitted to replace a section of corroded galvanized pipe, a special dielectric fitting called a " union " must be used to join the two types of pipes ; otherwise the presence of water in contact with differing metals creates an electrical current that can cause " galvanic corrosion ".
The electrical and thermal conductivity of metals originate from the fact that their outer electrons are delocalized.
The electrical conductivity, as well as the electrons ' contribution to the heat capacity and heat conductivity of metals can be calculated from the free electron model, which does not take the detailed structure of the ion lattice into account.
The metals are held together by metallic bonding, which confers distinctive physical properties such as their shiny metallic lustre, ductility and malleability, and electrical conductivity.
Metallic bonding accounts for many physical properties of metals, such as strength, malleability, ductility, thermal and electrical conductivity, opacity, and luster.
It is found in nature as an alloy, mostly in platinum ores ; its alloys with platinum, iridium, and other platinum group metals are employed in fountain pen tips, electrical contacts, and other applications where extreme durability and hardness are needed.
It has the highest electrical conductivity of all metals, even higher than copper, but its greater cost has prevented it from being widely used in place of copper for electrical purposes.
Semiconductors differ from metals in their characteristic property of decreasing electrical resistivity with increasing temperature.
Junctions between metals and n-type or p-type semiconductors, or between the two types of semiconductors, have asymmetric conduction properties, and semiconductor junctions can therefore be used to rectify electrical currents.
Electrons within the conduction band are mobile charge carriers in solids, responsible for conduction of electric currents in metals and other good electrical conductors.
Following Wiedemann – Franz law thermal conductivity of metals is approximately proportional to the absolute temperature ( in Kelvin ) times electrical conductivity.
In pure metals the electrical resistivity often increases proportional to temperature and thus thermal conductivity stays approximately constant.
In metals, thermal conductivity approximately tracks electrical conductivity according to the Wiedemann-Franz law, as freely moving valence electrons transfer not only electric current but also heat energy.
Electrons also conduct electric current through conductive solids, and the thermal and electrical conductivities of most metals have about the same ratio.
In their efforts to exploit the destructive effects of an electrical discharge, they developed a controlled process for machining of metals.
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