Additive Principle (Series Hall Potentials)

The additive principle is Palmer H. Craig's finding, reported in his 1926 Physical Review paper, that stacking thin bismuth films so that their Hall potentials are placed in series adds those potentials. Craig reported that the series Hall potentials of stacked films agree well with the calculated sum of the individual films, while noting in the source that the additive result "has little application where quantitative readings of a high degree of accuracy are desired."

Role in the device

The additive principle is the basis of Craig's rectifier claim. Because each film produces only a small Hall emf — on the order of tens of microvolts — summing many films in series is the route by which the patent US1822129 — System & Apparatus Employing the Hall Effect claims to reach usable voltages. The patent's stacked-plate design connects plates in parallel at their ends and in series along the transverse axis, so that the longitudinal current is shared while the transverse Hall potentials sum.

Reported magnitudes

• About 50 µV per film.
• About 200 µV with transverse series connection, under 4 A at 60 Hz through a 12-turn coil.
• "Several volts for only one milliampere flowing through the field coil and longitudinally through the conductive films in parallel."

The source does not report any independent measurement of the additive principle outside Craig's own work and the patent's own figures.

See also

Hall-Effect Rectification, Thin Bismuth Film Preparation, comparisons/comparison-craig-hall-effect-claims-vs-evidence.