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- Title
MEASURING DIPOLE MOMENT OF A PERMANENT MAGNET AND THE EARTH'S LOCAL MAGNETIC FIELD.
- Authors
Getaneh, Misganaw; Wimbish, Wallis A.
- Abstract
As a means to determine the dipole moment of a permanent magnet, as well as the horizontal component of the Earth's local magnetic field, a cylindrical neodymium magnet with axial magnetic dipole moment is suspended from a thin vertical string with its axis horizontal. In the absence of other magnetic fields, it settles along the Earth's magnetic north-south line. A Helmholtz coil set was placed around the magnet, with its symmetry axis parallel to the Earth's field and with the magnet at its center. Rotating the magnet about an axis through the string results in a restoring torque, which when released, results in oscillations of the magnet with frequency that depends on the coil current. The frequency was measured for several coil currents. The resulting frequency versus current data is used to determine the dipole moment of the magnet. The horizontal component of the Earth's magnetic field is also determined from the same data. Measurement of the Earth's field thus obtained is in good agreement with values obtained using other methods. The dipole moment of the magnet was also measured using a second method that involves measurement of terminal speed of the magnet as it falls in a vertical cylindrical aluminum tube against a magnetic braking force of current induced in the tube.
- Subjects
DIPOLE moments; PERMANENT magnets; MAGNETIC fields; HELMHOLTZ equation; ALUMINUM tubes; MAGNETIC brakes; EARTH (Planet)
- Publication
Journal of the Tennessee Academy of Science, 2010, Vol 85, Issue 2, p41
- ISSN
0040-313X
- Publication type
Article