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Unformatted text preview: Electricity and Magnetism I (P331) Homework 8 Due: Wednesday, November 18, 4:00 PM The next exam will be Friday, November 20 in class. 1. You’ve probably seen the demonstration device pictured below. Permanently magnetized rings (“donuts”) are free to move up and down along a central rod. Treat the rings as dipoles with mass M and dipole moment m . z x y (a) Suppose that two rings are placed with their dipole magnets back to back. Find an expression for z , the equilibrium distance between the rings. (b) Suppose now that a third ring is added as pictured above. Determine the ratio of the two sepa- rations: x/y . It is difficult to obtain a closed form solution, but you can still get a numerical answer. First write down an equation that contains x/y and no other variables. For example, if you define k ≡ x/y you should be able to write a function f ( k ) such that f ( k ) = 0. Then plot f ( k ) and pick out the correct solution. What is the approximate numerical value for x/y ?...
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