5: Hall Effect

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In this chapter we discuss another type of inductive energy conversion device, the Hall effect device. While these devices may be made from conductors, they are more often made from semiconductors, like silicon, which are easily integrated into microelectronics. The Hall effect was discovered using gold by Edwin Hall in 1879 [57]. The first practical devices were produced in the 1950s and 1960s when uniform semiconductor materials were first manufactured [57].

Hall effect sensors are used to measure some hard to observe quantities. Without external tools, humans cannot detect magnetic field. However, a small, inexpensive Hall effect sensor can act as a magnetometer. Also, the Hall effect can be used to determine if a semiconductor is n-type or p-type. One of the first applications of Hall effect devices was in computer keyboard buttons [57]. Today, Hall effect devices are used to measure the rotation speed of a motor, as flow rate sensors, in multiple types of automotive sensors, and in many other applications.

5.1: Physics of the Hall Effect
Hall effect devices are direct energy conversion devices that convert energy from a magnetic field to electricity. The physics behind these devices is described by the Lorentz force equation.
5.2: Magnetohydrodynamics
A magnetohydrodynamic device converts magnetic energy to or from electrical energy through the use of a conductive liquid or plasma. Similar to the Hall effect, the fundamental physics of the magnetohydrodynamic effect is described by the Lorentz force equation. The difference is that the magnetohydrodynamic effect occurs in conductive liquids or plasmas while the Hall effect occurs in solid conductors or solid semiconductors.
5.3: Quantum Hall Effect
Around a hundred years after the discovery of the Hall effect, the quantum Hall effect was discovered. Klaus von Klitzing discovered the integer quantum Hall effect in 1980 and won the physics Nobel prize for it in 1985.
5.4: Applications of Hall Effect Devices
A Hall effect device is a simple device. It is essentially a piece of semiconductor with leads connected and calibrated for use. For this reason, Hall effect devices are inexpensive, small, and readily available. As with most integrated circuits, these devices are durable and long lasting because they have no mechanical moving parts.
5.5: Problems

Thumbnail: Hall effect. (Public Domain; Hajder via Wikipedia)