School of Physics Lecture Demonstration Manual

Eb-10 Lenz’s Law (2 Coils on a Pipe)

Published: Tuesday 05 June 2007 - Updated: Tuesday 29 March 2011


To demonstrate the induced E.M.F when there is relative motion between a conductor and a magnetic field.



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Lenz's Law (2 Coils on a Pipe)


Lenz' Law (2 Coils on a Pipe)


The apparatus consists of a clear plastic pipe which has two coils placed approximately 50cm apart. The coils are each directly connected to an LED.

A Neodymium Boron magnet is dropped down the plastic pipe. As it passes the coils, it induces a current in the coils, which causes the LED’s attached to the coils to light up. The demonstration may be used in conjunction with the Eddy current pipe demonstration to illustrate that the falling magnet induces eddy currents that oppose the fall of the magnet.

Safety notes


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