LABORATORY INVESTIGATION OF GEOMAGNETIC DYNAMOS.
Final technical rept.,
NEWCASTLE-UPON-TYNE UNIV (ENGLAND)
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It is likely that the Earths magnetic field is maintained by a self-exciting dynamo mechanism in the liquid conducting core. This report describes an attempt to build a self-exciting homogeneous dynamo in the laboratory. By rotating two cylindrical ferromagnetic conductors in cylindrical holes in a stationary block of the same material with a thin layer of mercury to give electrical contact evidence was obtained of the existence of a critical velocity of rotation above which the system would be self-exciting. To reduce this critical velocity to an attainable value some inhomogeneity had to be introduced in the form of thin insulating layers. The behaviour of the model in its steady-state self-exciting condition is described large induced electric currents and magnetic fields were produced and appreciable power was dissipated as Joule heating. Qualitative explanations are suggested, but the behaviour is complicated by the saturation of the ferromagnetic conductor. Possible instability oscillations of the system could not be investigated because of the very large viscous damping of the mercury. Methods of reducing this damping are suggested. Author