An experiment is described in which a small permanent magnet is scattered by a second identical fixed magnet. The apparatus sits on an air table, so the scattered object can move with negligible friction. A ring of Hall effect switches surrounding the fixed magnet is used to determine the scattering angle. The experimental data are compared with numerical simulations and the form of the repulsive force between the two magnets is determined.
REFERENCES
1.
K. Krane, Modern Physics (Wiley, New York, 1983), pp. 154–160.
2.
R. Eisberg and R. Resnick, Quantum Physics of Atoms, Molecules, Solids, Nuclei, and Particles (Wiley, New York, 1985), 2nd ed., pp. 90–95.
3.
R. A. Serway, C. J. Moses, and C. A. Moyer, Modern Physics (Saunders College Publishing, Philadelphia, 1989), 2nd ed., pp. 109–116.
4.
R. A. Becker, Introduction to Theoretical Mechanics (McGraw–Hill, New York, 1954), Example 10-3, pp. 231–232.
5.
The air table was made from wood composite and laminate; these materials guaranteed that no eddy current drag forces would arise from the motion of the magnetic puck across its surface.
6.
Samarium—cobalt magnets, Part No. CR3054313 from Edmund Scientific, 60 Pearce Ave., Tonawanda, NY 14150-6711, 〈www.scientificsonline.com〉.
7.
Type 3604 Hall probe, sensitivity 0.044 mV G, Sensor Division, Sprague Electric Company, Concord, NH.
8.
Model 423 translation stage with model SM-25 micrometer, Newport Corp., 1791 Deere Ave., Irvine, CA 92606, 〈www.newport.com〉.
9.
Model 443 translation stage with model SM-50 micrometer, Newport Corp.
10.
Hall switches: Panasonic Part No. DN6852.
11.
Model ADC488, IOtech, Inc., 25971 Cannon Road, Cleveland, OH 44146, 〈www.iotech.com〉.
12.
HP VEE (Visual Engineering Environment), version 5.01, Agilent Technologies, 395 Page Mill Road, Palo Alto, CA 94303, 〈www.agilent.com〉.
13.
Strictly speaking, the calibration gives the most probable launch velocity vs micrometer setting. Because of very slight variability in the manual release of the puck, any single shot may have a velocity which differs from the calibration value by as much as a few percent.
14.
The conversion of an experimental to its normalized form, β, requires a particular value for the launch velocity corresponding to the case where the air puck exactly reaches the sensor circle when and then reverses back on its path. It was found that the velocity for this to happen was so small that the required separation of the puck from the repeller magnet exceeded the maximum travel of the micrometer.
15.
The values of were 1.21, 1.72, 2.59, 4.03, 6.38, 10.20.
16.
The values of were 1.2975, 2.1117, 3.6899, 6.6851, 12.3745, 23.2327.
17.
R. H. Good, Jr. and T. J. Nelson, Classical Theory of Electric and Magnetic Fields (Academic, New York, 1971), p. 228.
18.
J. D. Jackson, Classical Electrodynamics (Wiley, New York, 1962), p. 102.
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© 2004 American Association of Physics Teachers.
2004
American Association of Physics Teachers
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