The standard ampere is most accurately realized using a watt balance, but is in practice maintained via Ohm's Law from the units of electromotive force and resistance, the volt and the ohm, since the latter two can be tied to physical phenomena that are relatively easy to reproduce, the Josephson junction and the quantum Hall effect, respectively.

In a similar way, accurate AC / DC non-contact ammeters have been constructed using Hall effect magnetic field sensors.

This phenomenon arising due to the nature of charge carriers in the conductor came to be known as the Hall effect, but it was not properly explained at the time, since the electron was experimentally discovered 18 years later.

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.

Shortly after, in 1982, Störmer and Tsui observed the fractional quantum Hall effect where the conductivity was now a rational multiple of a constant.

The study of topological properties of the fractional Hall effect remains an active field of research.

Devices used for this include Hall effect sensors, current clamps, current transformers, and Rogowski coils.

* Hall effect current sensor transducers

In some contexts it is meaningful to speak of fractions of a charge ; for example in the charging of a capacitor, or in the fractional quantum Hall effect.

The quasiparticles of the fractional quantum Hall effect are also known as composite fermions, which are electrons with an even number of quantized vortices attached to them.

The Hall effect is the production of a voltage difference ( the Hall voltage ) across an electrical conductor, transverse to an electric current in the conductor and a magnetic field perpendicular to the current.

The Hall effect was discovered in 1879 by Edwin Herbert Hall while he was working on his doctoral degree at Johns Hopkins University in Baltimore, Maryland.

The Hall effect is due to the nature of the current in a conductor.

This cannot explain the opposite sign of the Hall effect observed.

As a result, the Hall effect is very useful as a means to measure either the carrier density or the magnetic field.

One very important feature of the Hall effect is that it differentiates between positive charges moving in one direction and negative charges moving in the opposite.

The Hall effect offered the first real proof that electric currents in metals are carried by moving electrons, not by protons.

The Hall effect also showed that in some substances ( especially p-type semiconductors ), it is more appropriate to think of the current as positive " holes " moving rather than negative electrons.

The sample inhomogeneity might result in spurious sign of the Hall effect, even in ideal van der Pauw configuration of electrodes.

For example, positive Hall effect was observed in evidently n-type semiconductors.

It will also create secondary Hall currents, and accelerate magnetospheric particles — electrons in the arcs of the polar aurora, and singly ionized oxygen ions ( O +) which contribute to the ring current.

* The less-known MHD with low magnetic Reynolds number and critical Hall parameter, involving weakly ionized gases in a non-equilibrium state ( i. e. where the electron temperature is higher than the gas temperature ) known as " cold plasmas ", which are mathematically handled with dyadic tensors in a 7-dimensional phase space.

Charles Corydon Hall, a New England engineer, arrived in Alexandria to help manage a steel mill just as its natural gas supply was exhausted around the turn of the 19th century.

The 1967 STP Oil Treatment Special on display at the Indianapolis Motor Speedway Hall of Fame Museum, with the Pratt & Whitney gas turbine shown.

By assuming that the material contains immobile positive ions and an " electron gas " of classical, non-interacting electrons, the Drude model was able to explain electrical and thermal conductivity and the Hall effect in metals, although it greatly overestimated the electronic heat capacity.

Pontoon Beach has built a new City Hall and Police Department in the last three years, and more hotels, restaurants, and gas stations have been also built.

Hall rifles leaked gas from the often poorly fitted action.

* The Jahrhunderthalle ( Hall of the Century ), is the former gas and power station of a steel mill built at the turn of the 20th century.

Emerson Hall, opened in 2001, is the campus's newest residence hall, featuring suite ( address ) s, card-access security, a main lounge with gas fireplace and Northwest wood beams, and an exercise center.

After a little " misunderstanding " ( according to Randolph brethren, the Eastern group used rather stronger language ) about the placement of a cupola on top of Stetson Hall as a vent for the gas lighting, the pot boiled over and East Randolph petitioned to be incorporated as a separate town.

The bulldozer also knocked out natural gas service to City Hall and the cement plant, and damaged a truck and part of a utility service center.

Tribes hire both members, other Indians and non-Indians in varying capacities ; they may run tribal stores, gas stations, and develop museums ( e. g., there is a gas station and general store at Fort Hall Indian Reservation, Idaho, and a museum at Foxwoods, on the Mashantucket Pequot Indian Reservation in Connecticut ).

* Roberta Hall ghost-On April 28, 1951 a gas tanker car stored on a siding of the Wabash Railroad tracks behind what was then Residence Hall exploded, sending steel chunks several blocks away.

On the southeast end is a Sunoco gas station, the Fire Station, the Town Hall, and the Litchfield Historical Society and Museum.

Until the Gas Showrooms was converted into a bank by Barclays, the combination of a Town Hall – a symbol of progressive local government, flanked by the gas and electric utilities, was unique.

The Lindbergh kidnapping-type case so scandalized the nation that it led to federal indictments, trials, and subsequent executions for both Hall and Heady, who died together in the Missouri gas chamber in December 1953.

Belfast Corporation ( now the council ) used their profits from the gas industry to pay for the construction of Belfast City Hall.

* Gazprom Hall – Exhibition hall featuring interactive exhibits about the world of gas supply.

In a plasma, the Hall parameter can take any value.

The Hall parameter, β, in a plasma is the ratio between the electron gyrofrequency, Ω < sub > e </ sub >, and the electron-heavy particle collision frequency, ν:

In a Hall thruster the attractive negative charge is provided by an electron plasma at the open end of the thruster instead of a grid.

One particular advantage of Hall thrusters, as compared to a gridded ion thruster, is that the generation and acceleration of the ions takes place in a quasi-neutral plasma and so there is no Child-Langmuir charge ( space charge ) saturated current limitation on the thrust density.

Construction of the JET machine itself began immediately after the completion of the Torus Hall, with the first plasma experiments in 1983.

* Kevin Peter Hall as The Predator, a member of a warrior race which hunts aggressive members of other species for sport, uses active camouflage, a plasma weapon and can see in the infrared spectrum.

It is the same thing with MHD accelerators, and high Hall effect MHD aerodynes must be disk-shaped, so the electric discharges in the plasma ( streamers ) can swirl freely around axis, for the Lorentz forces J × B to be centrifugal.

* In magnetized Low pressure discharges with high Hall parameter: creation of spiral currents, plasma confinement to wall and electrothermal instability cancellation by magnetic pressure gradient.