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The National MagLab is funded by the National Science Foundation and the State of Florida.

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Hall Effect

When a magnetic field is applied to a flowing current, it creates a weak but measurable voltage. This is the Hall effect.

Electrical currents are affected by magnetic fields. When a magnetic field is applied perpendicular to the flow of current, the field causes resistance in the current. This is a manifestation of the Lorentz force, which pushes the negatively charged electrons in the current in a direction dictated by the left hand rule

This movement of electrons results in a weak but measurable potential difference, or voltage, perpendicular both to the current flow and the applied magnetic field. This is known as the Hall effect, named after American physicist Edwin Hall, who discovered the phenomenon in 1879.

Instructions

  1. Observe the setup. The Hall Effect Tube is a vacuum with a trace of neon gas. Note the tube is connected to a battery and has current flowing, with the electrons depicted as yellow dots. A smaller tube intersecting the Hall effect tube is connected via electrodes to a Voltmeter.
  2. Use the slider to adjust the magnet position, moving it closer to the Hall Effect Tube.
  3. See how the path of the electrons changes course because of the resistance from the applied magnetic field.
  4. Notice how moving the magnet closer also produces a voltage perpendicular to the main current and measured by the voltmeter.
  5. Push the “flip magnet” button to see how this affects the movement of electrons and the voltage.

A similar effect is seen in semiconductors, where the Hall effect plays a large role in the design of integrated circuits on semiconductor chips. Some devices for measuring magnetic fields make use of semiconductors as the sensing elements and are called Hall probes.