Humans have utilized magnetized materials such as iron, magnetite, hematite, and other minerals for centuries. In particular, a thin iron bar was utilized as a compass for navigation. To explain the terrestrial magnetism, Gilbert (ca. 1600) first considered the planet Earth as a giant magnet. Since that time, magnetism became a subject for serious scientific studies, bringing about discoveries of many other magnetic materials. Due to their attractive and repulsive nature, each magnet was characterized by two distinct “poles,” named north and south poles (N- and Spoles), according to the way they interacted. These poles were recognized to exist always in pairs, and they were understood to be inseparable, unlike electric charges. Further, because of their delocalization on magnetized surfaces, polar charges were not easily measurable. Nevertheless, Coulomb (1785) defined magnetic poles according to the force between them in an idealized case, analogous to the static force between electric charges.
KeywordsIron Powder Ring Current Closed Path Charged Body Turn Number
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