School of Physics Lecture Demonstration Manual

Eb-9 Lenz’s Law with Aluminium Ring

Published: Wednesday 07 February 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.


· Suspended Aluminium Ring

· Retort stand and Boss head

· Neodymium Boron Magnet


Click on pictures to enlarge.

Lenz's Law Aluminium Ring

Lenz's Law Ring Pic 2


Lenz's Law with Aluminium Ring (Side view)

Lenz's Law with Aluminium Ring (Front View)


Lenz’s law states that a changing magnetic field threading a conductor induces an emf such that the direction of the current flow is to oppose the flux change. This demonstration illustrates Lenz’s law and by the motion of the ring, the direction of the current flow may be inferred. A strong magnet is slowly brought to pass through the central annulus of a suspended Aluminium ring. On approach the magnet is seen to be repelled illustrating that a like pole is induced in the suspended ring. Alternatively when the magnet is slowly removed the ring is seen to be attracted to the magnet illustrating that a current is flowing such that an opposite pole is being induced.

Safety notes


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