The Hall effect is the appearance of a transverse potential difference across a current-carrying conductor placed in a magnetic field perpendicular to the current. Charge carriers are deflected sideways by the Lorentz force, producing a voltage across the width of the conductor.
Formulation as used in the source
Palmer H. Craig's 1926 Physical Review paper defines the Hall coefficient as
R = Ed / IH
where R is the Hall coefficient, d the film thickness in cm, I the longitudinal current in abamperes, H the field in gausses, and E the net Hall emf. The patent US1822129 — System & Apparatus Employing the Hall Effect gives the equivalent relation
E = HI/d
Why bismuth
Bismuth is a semimetal with a long carrier mean free path and large magnetoresistance, properties documented in the later bismuth-film literature appended to the source. Craig's 1926 paper selected bismuth and tellurium because they have the highest Hall coefficient of the ordinary metals. The source's appended bibliography documents decades of later work on bismuth films — quantum size effects, epitaxial growth, magnetotransport, nanowire quantum confinement — none of which tests Craig's device.
Related phenomena
The patent names the Corbino Effect — radial current in a disc under a perpendicular field producing a circular current — as a related phenomenon.
See also
Hall-Effect Rectification, Anomalous Low-Field Hall Coefficient in Bismuth, Additive Principle (Series Hall Potentials).
Source notes & attribution
- https://rexresearch.com/craig/craig.htm