HR: 1400h
AN: ED73B-05    [Abstracts]
TI: A Simple Demonstration of a General rule for the Variation of Magnetic Field with Distance
AU: * Kodama, K
EM: kdma@cc.kochi-u.ac.jp
AF: Center for Advanced Marine Core Research, Kochi University, Monobe B-200, Kochi, 783-8502, Japan
AB: Most science students have some basic knowledge about magnets: magnetic poles attract or repel, depending on their polarity; the shorter the distance to the magnet, the greater the magnetic force. However, the specific magnetic force-distance relationship seems to confuse students. Many students appear to believe, mistakenly based on analogy to the electrostatic field or to gravity, that the force between magnets follows the familiar inverse-square law. It is difficult to teach them that the direction and magnitude of a magnetic field varies in quite a different manner from other interacting forces. I propose an educational demonstration illustrating the variation in magnitude of a magnetic field with distance, allowing students to grasp the idea of magnetic poles and dipoles. The method uses an ordinary geologic compass, a small circular magnet, and a bar magnet about 60 cm long. The small magnet is similar to those commonly used on household bulletin boards or refrigerator doors. The long bar magnet is a steel bar magnetized by a long solenoid coil with the application of a small current. The experiment is unique in that it is designed to permit students to infer a general law from their observations and requires no special instruments. The principle of this experiment is based on electromagnetism but is more readily understood, as it uses only ratios of measured properties. Some logarithmic and trigonometric calculations, easily computed with a pocket calculator, are required. No special calculations requiring a computer are necessary.
DE: 0825 Teaching methods
DE: 0845 Instructional tools
DE: 0850 Geoscience education research
SC: Education and Human Resources [ED]
MN: 2009 Joint Assembly