Incoming links: Hall effect
The voltage changes perpendicular to the current when magnetic field is applied.
Hall effect experimental diagram
. Source. The Hall effect refers to the produced voltage , AKA on this setup.
An intuitive video is:
The key formula for it is:where:
- : current on x direction, which we can control by changing the voltage
- : strength of transversal magnetic field applied
- : charge carrier density, a property of the material used
- : height of the plate
- : electron charge
Applications:
- the direction of the effect proves that electric currents in common electrical conductors are made up of negative charged particles
- measure magnetic fields, TODO vs other methods
Other more precise non-classical versions:
Implementations:
- Hall effect based, i.e. a Hall effect sensor
- SQUID device
Quantum version of the Hall effect.
As you increase the magnetic field, you can see the Hall resistance increase, but it does so in discrete steps.
Gotta understand this because the name sounds cool. Maybe also because it is used to define the fucking ampere in the 2019 redefinition of the SI base units.
At least the experiment description itself is easy to understand. The hard part is the physical theory behind.
TODO experiment video.
The effect can be separated into two modes:
- Integer quantum Hall effect: easier to explain from first principles
- Fractional quantum Hall effect: harder to explain from first principles
- Fractional quantum Hall effect for : 1998 Nobel Prize in Physics
- Fractional quantum Hall effect for : one of the most important unsolved physics problems as of 2023