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.

* Gate ( G ), the terminal that modulates the channel conductivity.

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.

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.

The term " enhancement mode " refers to the increase of conductivity with increase in oxide field that adds carriers to the channel, also referred to as the inversion layer.

In the less common depletion mode MOSFET, described further later on, the channel consists of carriers in a surface impurity layer of opposite type to the substrate, and conductivity is decreased by application of a field that depletes carriers from this surface layer.

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:

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 ∞.

Although undoubtedly true for small temperature gradients, strictly proportional behavior will be lost when real materials ( e. g. ones having a thermal conductivity that is a function of temperature ) are subjected to large temperature gradients.

Fourier's Law provides a simplified one-dimensional description of the variation in heat flow Q as a function of thermal conductivity k and thermal gradient dT / dz:

The water content is very important in vadose zone hydrology, where the hydraulic conductivity is a strongly nonlinear function of water content ; this complicates the solution of the unsaturated groundwater flow equation.

The depth of the halocline is a function of several factors: climate and specifically how much meteoric water recharges the aquifer, hydraulic conductivity of the host rock, distribution and connectivity of existing cave systems and how effective these are at draining water to the coast, and the distance from the coast.

Ellipsometry can probe the complex refractive index or dielectric function tensor, which gives access to fundamental physical parameters and is related to a variety of sample properties, including morphology, crystal quality, chemical composition, or electrical conductivity.

This formulation of the scale-space representation L means that it is possible to interpret the intensity values of the image f as a " temperature distribution " in the image plane and that the process which generates the scale-space representation as a function of t corresponds to heat diffusion in the image plane over time t ( assuming the thermal conductivity of the material equal to the arbitrarily chosen constant ½ ).

Lock-in detection and modulation techniques are used to find the conductivity, because the tunneling current is a function also of the varying tip-sample spacing.

The thermal conductivity of zirconium metal and uranium dioxide as a function of temperatureUranium dioxide is a black semiconductor solid.

The vapor core reactor provides a hotter-than-most fluid with potential for adequate thermal equilibrium conductivity and duct velocities.

Measurements commonly made on-site and in direct contact with the water source in question include temperature, pH, dissolved oxygen, conductivity, oxygen reduction potential ( ORP ), turbidity, and Secchi disk depth.

It has the lowest thermal conductivity and lowest ionization potential of all the non-radioactive noble gases.

The low thermal conductivity minimizes thermal losses in the lamp while in the operating state, and the low ionization potential causes the breakdown voltage of the gas to be relatively low in the cold state, which allows the lamp to be easily started.

Mathematically, the problem of recovering conductivity from surface measurements of current and potential is a non-linear inverse problem and is severely ill-posed.

There are other potential uses for EEG and MEG such as charting rehabilitation and improvement after trauma as well as testing neural conductivity in specific regions of epileptics or patients with personality disorders.

When a high enough potential is applied to the diode, the charge carrier density along the cathode becomes unstable, and will develop small slices of low conductivity and high field strength which move from the cathode to the anode.

where is the potential at radius from the source or sink, which passes current through a medium with conductivity.

The conductivity is varied by the electric field that is produced when a voltage is applied between the gate and source terminals ; hence the current flowing between the drain and source is controlled by the voltage applied between the gate and source.

The conductivity of the semiconductor changed only by a small fraction of the expected amount when the field was applied, which John Bardeen ( another member of Shockley's division ) suggested was due to the existence of energy states for electrons on the surface of the semiconductor.

Electroporation, or electropermeabilization, is a significant increase in the electrical conductivity and permeability of the cell plasma membrane caused by an externally applied electrical field.

Various additives are often applied to increase the conductivity of such systems.

The dependence of the current density on the applied electric field is essentially quantum mechanical in nature ; ( see Classical and quantum conductivity.

For read-out, a voltage intermediate between the possible threshold voltages is applied to the CG, and the MOSFET channel's conductivity tested ( if it's conducting or insulating ), which is influenced by the FG.

Most commonly applied to archaeology are magnetometers, electrical resistance meters, ground-penetrating radar ( GPR ) and electromagnetic ( EM ) conductivity meters.

The stronger the applied magnetic field, or the greater the electrical conductivity of the conductor, or the faster the field changes, then the greater the currents that are developed and the greater the fields produced.

As with all the other types of FETs, a voltage applied to the gate alters the conductivity of this layer.

Small amounts have begun to be sold as thermal grease to computer enthusiasts ; it has a much better heat conductivity compared to more standard thermal pastes ( allowing hot chips such as CPUs and GPUs to run several degrees cooler ), but needs to be applied more carefully than the electrically isolating standard greases, since spills can cause short circuits.

The geophysical methods most commonly applied to archaeology are magnetometers, electrical resistance meters, ground-penetrating radar ( GPR ) and electromagnetic ( EM ) conductivity.

The current density j is observed to be proportional to the applied electric field and follows Ohm's law where the prefactor is the specific electrical conductivity.

The Lorentz reciprocity theorem describes this case as well, assuming ohmic materials ( i. e. currents that respond linearly to the applied field ) with a 3 × 3 conductivity matrix σ that is required to be symmetric, which is implied by the other conditions below.

If this external current is in a material with a conductivity σ, then it corresponds to an externally applied electric field where, by definition of σ: