Current consists of the movement of many small charge carriers, typically electrons, holes, ions (see Electromigration) or all three. The Hall effect is due to the nature of the current in a conductor. įurther 'Hall effects' may have additional physical mechanisms but are built on these basics. The superposition of multiple Hall effects may be realized by placing multiple voids within the Hall element, with current and voltage contacts on the boundary of each void. (For simplicity, imagine the contacts on the boundary of the void lined up with the ordinary-configuration contacts on the exterior boundary.) In such a combined configuration, the two Hall effects may be realized and observed simultaneously in the same doubly connected device: A Hall effect on the external boundary that is proportional to the current injected only via the outer boundary, and an apparently sign-reversed Hall effect on the interior boundary that is proportional to the current injected only via the interior boundary. Next, imagine placing a rectangular void within this ordinary configuration, with current-contacts, as mentioned above, on the interior boundary of the void. This develops a Hall voltage, in a perpendicular magnetic field. First imagine the 'ordinary' configuration, a simply connected (void-less) thin rectangular homogeneous element with current-contacts on the (external) boundary. Superposition of these two forms of the effect, the ordinary and void effects, can also be realized. It depends only on the current injected from within the void. It exhibits apparent sign reversal in comparison to the 'ordinary' effect occurring in the simply connected specimen. The effect becomes observable, in a perpendicular applied magnetic field, as a Hall voltage appearing on either side of a line connecting the current-contacts. The charge then flows outside the void, within the metal or semiconductor material.

The term ordinary Hall effect can be used to distinguish the effect described in the introduction from a related effect which occurs across a void or hole in a semiconductor or metal plate when current is injected via contacts that lie on the boundary or edge of the void. Eighteen years before the electron was discovered, his measurements of the tiny effect produced in the apparatus he used were an experimental tour de force, published under the name 'On a New Action of the Magnet on Electric Currents'. In 1879 Edwin Hall was exploring this interaction, and discovered the Hall effect while he was working on his doctoral degree at Johns Hopkins University in Baltimore, Maryland. One such question was about the details of the interaction between magnets and electric current, including whether magnetic fields interacted with the conductors or the electric current itself. While Maxwell's paper established a solid mathematical basis for electromagnetic theory, the detailed mechanisms of the theory were still being explored. The modern theory of electromagnetism was systematized by James Clerk Maxwell in the paper ' On Physical Lines of Force', which was published in four parts between 18.

Electrical polarity