PURPOSE: To model the behavior of a magnetic material in a magnetic field.
DESCRIPTION: The array of compasses, representing magnetic domains in a sample of magnetic material, is positioned in the center of the Helmholz coils on the overhead projector. Using a small bar magnet the compasses are de-aligned into a state of relative disorder. As the field of the Helmholtz coils is increased, more of the small magnets flip into alignment with the applied field. This is a model of the domains flipping into alignment in a sample of magnetic material as the magnetic field is increased. This effect, known as the Barkhausen effect, is shown directly in Demonstration J7-24: BARKHAUSEN EFFECT.
SUGGESTIONS:
REFERENCES: (PIRA 5G20.30)
EQUIPMENT: Array of compasses with Helmholtz coils on overhead projector.
SETUP TIME: 5 min.
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