The development of teaching material using an experiment to produce cognitive disharmony

概要

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It is generally accepted that a repulsive force exists between homopolar magnets. We have, however, encountered aprocess that is different from the generally accepted repulsive force and use this phenomenon in a teaching experimentthat illustrates cognitive disharmony. The repulsive force acts between homopolar magnets only when the differencein magnetic flux density between magnets is roughly equivalent. And this repulsive force changes depending on thedistance between the magnets. On the other hand, the force which acts with decreasing distance between magnets,changes from a repulsive force to an attractive one when the difference in magnetic flux density between the magnetsis large (one magnet several times stronger than the other). A decrease in the magnetic flux density and reversal ofpolarity appears in the magnet where the magnetic flux density is lowest. It is clear that the force which acts betweenmagnets changes from repulsion to attraction or vice versa for separations of 1 mm or less. The experimental resultsconfirmed this phenomenon as an effective teaching tool, especially for teaching how to handle cognitive disharmony.
2010-07-14