E&M > Electromagnetic Induction > Induced Currents and Forces
DCS# 1C30.22
ELECTROMAGNETIC INDUCTION AND FREE FALL
APPARATUS
glass tube with coils
202-20-C
strong cylindrical magnet
202-20-D5
storage scope
202-08-B
sandbox
202-20-C
DESCRIPTION
Drop the magnet through the tube. The induced voltage looks like this:
NOTES
Centers of coils are 30 cm apart.
Use the sandbox to catch the magnet. If bottom of tube is too low, magnet may bounce back and break it.
Scope settings:
0.2 V/div
50 ms/div
triggering:
single sweep mode
internal source
AC coupling
level ~1 o'clock
Or replace the storage scope with a computer running LoggerPro.
A java applet of a magnet falling through a conducting ring, which shows magnetic field lines and monitors the eddy current, can be found here:
http://web.mit.edu/jbelcher/www/java/falling/falling.html
.
REFERENCES
J.S. Huebner and J.T. Humphries. Am.J.Phys. 42, 870 (1974).
TPT 12 (2), 115.