Your job is to design and assess a personal power generator based on the Faraday

Question

Your job is to design and assess a personal power generator based on the Faraday Effect. The coil will be used to charge a capacitor which will be used to power an MP4 player (an i-thingy). The generator will use a small rare earth magnet with a magnetic field strength of 1.0 T. The magnet is 0.50 inches on a side and is mounted on a shaft so that it can rotate as shown. The magnet sits in the center of a fixed square coil of wire with inner side length of L=0.51 inches. The magnetic field lines come out normal to the larger flat surfaces of the magnet. Assume that the magnet and coil are both thin enough so the geometry is simple and the fields continue straight out from the surface beyond the coil wires (do not diverge).

The magnet can be rotated by a hand crank at 300 revolutions per minute. Find the amplitude of the emf that can be generated with a single turn in the coil.

Explanation / Answer

B = magnetic field = 1 T

A = area = 0.50 x 0.51 in2 = 0.000165 m2

W = 300 rev/min = 300 x 2pi /60 = 31.4 rad/s

so amplitude of EMF = BAW = 1 * 0.000165 * 31.4 = 5.2 x 10-3 volts

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