Describe Hall Effect? Briefly discuss physical origin and uses of Hall Effect?

Ans:

If a conducting bar is placed in a magnetic field B ⊥ to its axis and if a current flows through the bar in axial direction, then an electric field E is developed which is ⊥ to both I and B. This effect is termed as Hall Effect.

Its physical origin follows from the Boltzmann Transport phenomenon.  It's used to get carrier density and the sign of the carriers involved (whether holes or electrons).