N.P. Armitage notes on Hall effect experiments.
In 1878, Edwin Hall, a graduate student here at Hopkins, was reading Maxwell's 'Treatise on Electricity and Magnetism', which had just appeared in 1873. Maxwell discussed the deflection of a electronic currents by a magnetic field and wrote "It must be carefully remembered that the mechanical forces which urges a conductor ... acts, not on the electronic current, but on the conductor which carries it." If you are confused by this statement, then your instincts are good. It doesn't make any sense!
Hall was similarly confused (and skeptical) and asked Henry Rowland, who replied that he too doubted the truth of Maxwell's statement. In the past he had tried a quick experiment, but had been without success in making reliable measurements.
Following some suggestions of Rowland, Hall made a new attempt and after some effort discovered the effect that now bears his name. In this lab you will follow in the footsteps of your esteemed predecessor and perform this seminal and foundational experiment of condensed matter physics.
It is now a routine characterization technique for electronic properties of solids. It provides an introduction to computer acquisition, magnetic probes, and transport experiments in solid which are really the bread and butter of condensed matter experiments. It is only a slight overstatement to say that all other experiments one does in condensed matter are simply higher order experiments to shed light on interesting phenomena observed in transport.
Most information you need to perform this lab can be found at the links below.
-DO NOT leave large currents running in the Hall bar or the magnet for long periods of time! The wires cannot withstand the resulting heating for extended periods.
- You will find that you get much better results for silver than for tungsten. This is likely due to the larger resistance of tungsten and hence larger heatload with current going through it. Any speculation why this is a problem? What might you do to remedy it?
-Note while performing this experiment I got very different Hall coefficient for tungsten than in Steve Wonnell's write-up below. The accepted value is a little higher than Steve got (a reference below).
Useful Links:
-Dr. Steve Wonnell’s write up on the Leybold Hall effect apparatus.
-Instruction by Mariko Ninomiya on performing the lab in .pdf (and in .ps).
-Prof. Petar Maksimovic's notes on the Hall effect measurement.
- Edwin Hall's original paper "On a New Action of the Magnet on Electric Currents" - Notice his interesting and colloquial narrative style. Appreciate, but don't necessarily imitate it!
- Another old reference on "The Hall effect and allied phenomena in rare metals and alloys." - details on some parameters of tungsten.
- Wikipedia's entry on the Hall effect.
modified N.P. Armitage 2006-9-21