Lenz's Law - Magnet In Aluminum Tube

Purpose

To demonstrate Lenz's law dramatically.
 

Equipment

Two linear magnet arrays, aluminum rod, mounted six-foot aluminum tube with magnet catcher.

 

Images

k2-42

Description

This is a commercial device purchased from Pasco Scientific. Two arrays of magnets, containing five strong disc magnets each with small aluminum spacers between the magnets, are dropped through a vertical aluminum tube. One set,having its poles North-to-South, has very little external field, and falls very quickly through the tube. The other set, having its poles arranged North-to-North, then South-to South, etc, has a large external field. As it falls it induces large currents in the aluminum tube. According to Lenz's law, these currents interact with the falling magnet array so as to oppose
 

References

Jhules A. M. Clack and Terrance P. Toepler, Magnetic Induction Experiment, TPT 28, 236-238, (1990).