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Reprinted by permission of Dick Berg, University of Maryland, for use on this website.

The demonstrations contained and referenced herein are listed for the purposes of cataloging and describing physics demonstrations which should be conducted only under the direction of a trained instructional support professional or physicist. These demonstrations are not presented for the purpose of being conducted by persons unconnected to this Facility and/or persons not consulting with or being supervised by the recognized instructional support professional or physicist and his/her staff. The University is responsible only for those demonstrations carried out using its own equipment using established safety and scheduling policies, and bears no responsibility for those choosing to use this source material for their own purposes. All demonstrations described and contained herein are public domain, and can also be found in reference materials in libraries, bookstores, and electronic sources.

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In most stars the inner core is rotating faster or slower than the outer layer so that there is a readily detectable shear force. If a star has a variable magnetic field and this field increases some of the outer layer are tied to the inner core by the magnetic field and forced to rotate at the same speed. Since total angular momentum is conserved there is a detectable change in the rate of rotation for both systems.

Our version of this is to drop a heavy small diameter rotating mass onto a lighter larger diameter rotating mass. The small diameter plate with the lead strips is approximately 3 times heavier than the rotating air table. (Small diameter plate contains about 75 % of the mass of the total system of the two plates.) By gently dropping the heavy mass onto the lighter mass you may demonstrate frictional slippage as the two masses achieve a common rotation rate. NOTE: There are some sharp edges here so it is advisable to wear gloves when trying to establish your initial rotation rates.