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conductivity and is
Thermal conductivity is directly traceable to the material's porous, air-cell construction which effectively traps air or a gas in the maze of minute bubbles which form its composition.
Above, h is enthalpy, k is the thermal conductivity of the fluid, T is temperature, and is the viscous dissipation function.
Diamond has a very low electrical conductivity, while graphite is a very good conductor.
Since the electrical conductivity is low, gases are dielectrics or insulators.
Often this is stated as: full bands do not contribute to the electrical conductivity.
Current density ( current per unit area ) J in a material is proportional to the conductivity σ and electric field in the medium:
The field-effect transistor ( FET ) is a transistor that uses an electric field to control the shape and hence the conductivity of a channel of one type of charge carrier in a semiconductor material.
The conductivity of the channel is a function of potential applied across the gate and source terminals.
LB is relatively new and is ineffective in resolving fragments larger than 5 kbp ; However, with its low conductivity, a much higher voltage could be used ( up to 35 V / cm ), which means a shorter analysis time for routine electrophoresis.
In a plasma, helium's electrons are not bound to its nucleus, resulting in very high electrical conductivity, even when the gas is only partially ionized.
The nutrient solution is changed either on a schedule, such as once per week, or when the concentration drops below a certain level as determined with an electrical conductivity meter.
In a slightly more complex system, it is automated with a delivery pump, a timer and irrigation tubing to deliver nutrient solution with a delivery frequency that is governed by the key parameters of plant size, plant growing stage, climate, substrate, and substrate conductivity, pH, and water content.
In hydrology the harmonic mean is used to average hydraulic conductivity values for flow that is perpendicular to layers ( e. g. geologic or soil ) while flow parallel to layers uses the arithmetic mean.
This apparent difference in averaging is explained by the fact that hydrology uses conductivity, which is the inverse of resistivity.
The energy efficiency of induction motors is greatly influenced by the conductivity of the winding material.
The coronal discharges identified as Kirlian auras are the result of stochastic electric ionization processes, and are greatly affected by many factors, including the voltage and frequency of the stimulus, the pressure with which a person or object touches the imaging surface, the local humidity around the object being imaged, how well grounded the person or object is, and other local factors affecting the conductivity of the person or object being imaged.
Since growth is controlled by heat diffusion, anisotropy in thermal conductivity favors growth in specific directions, which has also an effect on the final shape.
The value of ' α ' is determined by conductivity measurements by applying the formula Λ / Λ ∞.

conductivity and varied
By adding impurity to pure semiconductors, the electrical conductivity may be varied not only by the number of impurity atoms but also, by the type of impurity atom and the changes may be thousand folds and million folds.
Calzecchi found that the conductivity of metal powder varied depending on the incidence of radio waves.

conductivity and by
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.
One of the first studies of condensed states of matter was by English chemist Humphry Davy, when he observed that of the forty chemical elements known at the time, twenty-six had metallic properties such as lustre, ductility and high electrical and thermal conductivity.
The quantum Hall effect was discovered by Klaus von Klitzing in 1980 when he observed the Hall conductivity to be integer multiples of a fundamental constant.
Construction of a high temperature proton exchange membrane fuel cell | PEMFC: Bipolar plate as electrode with in-milled gas channel structure, fabricated from conductive composite material | composite s ( enhanced with graphite, carbon black, carbon fiber, and / or carbon nanotube s for more conductivity ); Porous carbon papers ; reactive layer, usually on the polymer membrane applied ; polymer membrane. Condensation of water produced by a PEMFC on the air channel wall.
Properties such as shear strength, stiffness hydraulic conductivity, and coefficient of consolidation may be significantly altered by sample disturbance.
Those ions are surrounded by de-localized electrons, which are responsible for the conductivity.
Some metals form a barrier layer of oxide on their surface which cannot be penetrated by further oxygen molecules and thus retain their shiny appearance and good conductivity for many decades ( like aluminium, magnesium, some steels, and titanium ).
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.
Gypsum has very low thermal conductivity and maintains a low temperature when heated as it loses that heat by dehydrating ; as such, gypsum is used as an insulator in materials such as plaster and drywall.
Schematic representation of a planetary dipole magnetic field in a vacuum ( right side ) deformed by a region of plasma with infinite conductivity.
Chapman and Bartels ( 1940 ) illustrated this concept by postulating a plate with infinite conductivity placed on the dayside of a planet ’ s dipole as shown in the schematic.
Radar signals are reflected especially well by materials of considerable electrical conductivity — especially by most metals, by seawater, by wet land, and by wetlands.
The increase in conductivity is also taken advantage of in RF engineering at VHF and higher frequencies, where conductors often cannot be scaled by 6 %, due to tuning requirements, e. g. cavity filters.
The electronic properties and the conductivity of a semiconductor can be changed in a controlled manner by adding very small quantities of other elements, called “ dopants ”, to the intrinsic material.

conductivity and electric
Its high malleability, ductility, resistance to corrosion and most other chemical reactions, and conductivity of electricity led to many uses of gold, including electric wiring, colored-glass production and even gold leaf eating.
* On the power factor and conductivity of dielectrics when tested with alternating electric currents of telephonic frequency at various temperatures ( 1912 ) Gresham, 82 pages, ASIN: B0008CJBIC
Semiconductor conductivity can be controlled by introduction of an electric or magnetic field, by exposure to light or heat, or by mechanical deformation of a doped monocrystalline grid ; thus, semiconductors can make excellent sensors.
Another type of transistor, the field effect transistor, operates on the principle that semiconductor conductivity can be increased or decreased by the presence of an electric field.
An electric field can increase the number of free electrons and holes in a semiconductor, thereby changing its conductivity.
The gate electrode is charged to produce an electric field that controls the conductivity of a " channel " between two terminals, called the source and drain.
where μ is the magnetic permeability, ε is the electric permittivity and σ is the electrical conductivity of the material the wave is travelling through.
where J is the current density at a given location in a resistive material, E is the electric field at that location, and σ is a material dependent parameter called the conductivity.
The dependence of the current density on the applied electric field is essentially quantum mechanical in nature ; ( see Classical and quantum conductivity.
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.
Electrical conductivity or specific conductance is the reciprocal quantity, and measures a material's ability to conduct an electric current.
On the surface of Titan, the electrical conductivity and permittivity ( i. e., the ratio of electric displacement field to its electric field ) of the surface material was measured.
This new apparatus led to an abundance of new findings, including a study of the compressibility, electric and thermal conductivity, tensile strength and viscosity of more than 100 different compounds.
* Electrical conductivity, a measure of a material's ability to conduct an electric current
Using Ohm's law, J σE, which relates current density J to electric field E in terms of a material's conductivity σ, and assuming isotropic homogeneous conductivity, the equation can be written as
Continuing his experiments at the University of Christiania ( 1891-1892 ), he proved experimentally the influence which the conductivity and the magnetic properties of the metallic conductors exert upon the electric oscillations, and measured the depth to which the electric oscillations penetrate in metals of different conductivity and magnetic permeability ( the “ skin effect ”).

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