Purpose:Describes the magnitude and the direction of the drag, called magnetic damping produced from Eddy currents.
Plug the setup to the wall outlet and set the voltage to its maximum. Then increase the current all the way up. Move the aluminum saw through the gap between magnets and feel the damping force. Drop the rings through the magnetic field, see how long will it take to drop through.
The same set up can also use with a knife switch in the circuit to show back emf when breaking an inductive circuit. You get a nice plasma arc across the knife switch contacts.