The Restless universe
|Introduction to The restless Universe|
1 The lawful Universe2 The clockwork Universe
Other titles in the Physical World series
4 The intangible Universe
4.1 Electromagnetism and fields
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Faraday, like others, was willing to accept this situation as far as a purely attractive force like gravity was concerned, or even for a force that could be attractive or repulsive like Coulomb's, but Faraday's own invention of the electric motor showed that the magnetic force on an electric current was not simply attractive or repulsive, it could cause rotation (see Figure 1.18). Faraday felt that for a wire to rotate around a magnet there had to be something, produced by the magnet but present at the location of the wire, that pushed the wire to one side rather than another. It was this agency, filling the space around the magnet, that Faraday eventually came to call a magnetic field.
Faraday's views about the nature of the magnetic field changed over time; for complex reasons, he spoke about his field as being different from an ether. Whatever his precise views, Faraday was convinced that fields held the key to understanding magnetic and electrical phenomena. He certainly felt that the curved pattern of lines revealed by sprinkling iron filings onto a sheet of paper placed over a magnet
When Maxwell started to work on electromagnetism he studied Faraday's experimental researches and, unlike most of his contemporaries, was impressed by the notion of a field. However, Maxwell had his own reasons for believing in an ether. In particular, he believed that an ether was necessary to account for the propagation of light, which was generally regarded as a kind of wavelike disturbance and was therefore thought to require a medium just as ocean waves require water. Maxwell therefore decided to combine Faraday's field ideas with the ether concept. He set out to treat electricity and magnetism in terms of fields that were themselves interpreted as manifestations of pressure, tension and motion within the ether.
Relevant LinksA note on powers of ten and significant figures
|S207 The Physical World|