School of Physics Lecture Demonstration Manual

Eb-8 Lenz's Law

Published: Tuesday 14 March 2006 - Updated: Tuesday 29 March 2011


To demonstrate the induced e.m.f when there is relative motion between a conductor and a magnetic field.



Click on pictures to enlarge.

Lenz's Law Pic


Lenz's Law


Two weights of similar appearance are allowed to drop inside an aluminium pipe. The time to fall through the pipe is radically different for the two weights. One of the weights is actually a strong magnet and induces eddy currents in the pipe as it falls. Lenz's law specifies that the direction of the induced currents is such as to oppose the motion and hence the long time needed to fall through the pipe (10 sec)

Safety notes


top of page