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When the yoke magnet is rotated, the non-magnetic brass ring appears locked and spins with the motion of the magnet.
This is a demonstration for Faraday's and Lenz's Laws. The yoke magnet is supported by a ring of ball bearings between the white and red plate, which allows the magnet to spin in the vertical axis. As it spins, the non-magnetic brass ring appears locked, and spins with the motion of the magnet. The change in the magnetic environment surrounding the ring causes an electromotive force to be induced in the ring (Faraday's Law). This EMF induces a current in the ring which generates a magnetic field that directly opposes this change in external magnetic field (Lenz's Law), thus conserving the magnetic flux through the ring. Faraday's Law can be expressed as the following: Voltage Induced= -N∆BA/t Where N is the number of turns of current allowing material (in this case, N=1, since it is just a ring, and not any sort of coil), B is the magnitude of the external Magnetic Field, and ∆A/t is the rate of change of area into or out of the magnetic field.
Demo room information