Ipendulum‘m delighted to announce that our new paper, “Predicting the influence of plate geometry on the eddy-current pendulum” has just been published in the American Journal of Physics. This journal publishes material related to physics education and our paper concerns a familiar classroom demonstration called Van Waltenhofen’s pendulum (or the Eddy Current pendulum) to demonstrate Eddy currents. As we describe in the introduction:

“The bob of the pendulum is a non-ferromagnetic, solid conducting plate that swings between the poles of an electromagnet, generating circulating eddy currents. The dissipative eddy currents tend to oppose the motion of the bob, and hence damp the pendulum. The experiment is an example of magnetic braking, meaning when the magnet is turned off, the pendulum oscillates as a classic pendulum, damped only by air resistance and frictional forces in the hinge. When the magnetic field is switched on, the pendulum comes to a rapid stop.”

One of my classes was assigned the task of trying to quantitatively predict the damping coefficient from the shape of the bob—a much harder task than we expected! This paper is the result.


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