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[Phys-l] A trivium



Well, not only interesting (amusing) , but a simple prob. in SHM.

F. OSCILLATION OF A FERROMAGNETIC BODY INSIDE A LIQUID CONDUCTOR
In the course of our studies of instabilities of a mercury column, an amusing effect was found by floating a piece of metal on the surface of a horizontal mercury column. When a current (of approximately 1000 amps) was sent through the column, the piece of iron was pulled into the mercury and set into vertical oscillations approximately about the center of the mercury column. At the center of the column the magnetic field is clearly zero and the vertical field gradients on either side are directed toward the center line, thereby producing a linear restoring force on the piece of iron.
U. Ingard, D. S. Wiley


bc thinks the prob. is solved by symmetry -- analogy w/ the g force under the surface of a spherical mass.