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.
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