Speaker
Description
This research consisted of three objectives (1) to study the basic principles of magnetic rollers (2) to construct a demonstration about magnetic force using the motion of magnetic rollers, and (3) to analyze the motion of the magnetic rollers using high speed video analysis techniques. Each magnetic roller is constructed from Neodymium permanent magnets, rechargeable batteries, and aluminum foil. The magnetic roller motion is based on magnetic force and torque. It can move when the same magnetic poles are facing each other. These basic physics principles are used to design the demonstration. The demonstration and activity sheet were used to teach 30 students enrolled in the Fundamental Physics 2 course. They were first-year students in geology and second-year students in mathematics at Faculty of Science, Chiang Mai University. As results, most students struggled with using the right-hand law to determine the direction of torque. Finally, the rolling motions of the magnetic rollers were analyzed using high-speed video analysis technique and Tracker program. Values of angular acceleration and terminal velocity of the magnetic rollers were determined from the tracking position versus time. As a result, angular acceleration and terminal velocity depend on current and magnetic field strength. To predict the center-of-mass velocity as a function of time, the induced electromotive force (emf) in the magnetic rollers was derived using Faraday disk. The velocity as a function of time can be described by the equation v(t)=v_t (1-e^((-t)⁄T) ), which is consistent with the analysis results. However, the experimental results of terminal velocities were not in agreement with the predicted values. This might be the assumption that the magnetic field strength of the magnet is constant, which is not.
