Wires carrying current in a magnetic field experience a mechanical force perpendicular to both the current and magnetic field. André-Marie Ampère in the 1820s observed this underlying mechanism that led to the discovery of the Hall effect.[3] However it was not until a solid mathematical basis for electromagnetism was systematized by James Clerk Maxwell's "On Physical Lines of Force" (published in 1861–1862) that details of the interaction between magnets and electric current could be understood.

The magnetic effect of electric current was first observed by __________

In your own words, explain why the moving compass needle proved there was a magnetic field around the electric current.

Describe how the magnetic field around a straight current-carrying wire behaves.

Name the scientist who discovered the magnetic effect of electri

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. The charge then flows outside the void, within the metal or semiconductor material. 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. It exhibits apparent sign reversal in comparison to the "ordinary" effect occurring in the simply connected specimen. It depends only on the current injected from within the void.[8