Magnetostatics

The word ‘magnetic’ is said to be associated with the town of Magnesia in Asia Minor. In this region ‘stones’ have been found in ancient times that did attract chips of iron. The name of the mineral with the chemical formula \(\text{Fe}_2\text{O}_3\) is magnetite or lodestone In the long period between the ancient and the modern era only one additional feature was added to our knowledge of magnetism. The fact, that the earth has a magnetic field was discovered around 1600 and has been used since that time for navigation. The first systematic investigation of magnetism is due to Hans Christian Ørstedt. He found in 1820 that a magnetic needle was not only aligned by the magnetic stones, but also by electric currents in conductors: Electric currents produce magnetic fields (Fig. 5.1a,b).