The Hall Effect
The computer and all the equipment here is set up for the Hall effect lab
E.H. Hall first witnessed what is now called the
Hall effect in 1879. He found that if a current is put into a magnetic
field, the charges moving in the current will be accelerated to one side
or another in the material according to the Lorentz force. This will
cause one side of the material to have more negative charge or more positive
charge than the other, and will result in a potential difference, called
the Hall voltage. In this experiment, the student will use a computer
to see the Hall effect in two different Hall chips. To begin the
student must set up the circuit as outlined in the lab handout. Once
the correct connections have been made to the Hall probe (a piece of plexiglass
containing the Hall chip, this one made of germanium), the probe is inserted
into a magnetic field generated by Helmholtz coils. Then, following
the instructions on the computer program which accompanies this lab, the
student calibrates the ADC/DAC card (Analog to Digital and Digital to Analog
card). Again, following the program, the student will increase and
decrease the current through the Hall chip. Then, by plotting the
voltage versus the current, the student can determine whether the charge
carriers are electrons (- slope) or holes (+ slope). After another
calibration, the Hall probe can be used to measure magnetic field strengths.
Then the student will calculate the number density of the charge carriers,
the Hall coefficient and the ratio of the charge carrier density to the
atomic density. Finally, the student will repeat the experiment using
a second Hall probe.
