Hall effect sensors basically consist of a thin rectangular p-type semiconductor material, such as gallium arsenide (GaAs), indium antimonide (InSb), or indium arsenide (InAs), which pass a continuous current through themselves. When the device is placed in a magnetic field, the magnetic flux lines exert a force on the semiconductor material, which force deflects charge carriers, electrons, and holes to either side of the semiconductor plate. This movement of the charge carriers is the result of the magnetic force they undergo through the semiconductor material.
When these electrons and holes move to the side, a potential difference is created between the two sides of the semiconductor material by the accumulation of these charge carriers. Then, the motion of electrons through the semiconductor material is affected by an external magnetic field at right angles to it, and this effect is greater in flat rectangular materials.
The effect of generating a measurable voltage by using a magnetic field is called the Howard Hall's Hall effect, which was discovered after the 1870s. The basic physical principle of the Hall effect is Lorentz force. In order to produce a potential difference across the device, the magnetic flux lines must be vertical, (90 ø to the flow of current), and follow the correct polarity, usually an South Pole.
The Hall effect provides information about the type of magnetic pole and the magnitude of the magnetic field. For example, the South Pole causes the device to produce a voltage output, while the North Pole is ineffective. Generally, when no magnetic field is present, the Hall effect sensor and switch are designed to be in an "off" state (open circuit state). They only become "on" when subjected to a magnetic field of sufficient strength and polarity (closed circuit state).