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Just as Newton had been able to make gravity an effective part of the mechanistic world-view by declaring that the gravitational force between two point-like bodies was proportional to the product of their masses and the inverse square of their separation, so the French scientist Charles Coulomb (1736 - 1806) was able to do the same for electricity by showing that the electrical force between two point-like bodies was proportional to the product of their charges and the inverse square of their separation. In terms of symbols, this can be expressed as:
However, electrical charge can be positive or negative, and the electrical forces can be attractive or repulsive in accordance with the famous dictum

'like charges repel; unlike charges attract'

Forces between magnets could be treated in a similar way by using north and south magnetic poles in place of positive and negative charges.

The incorporation of electrical and magnetic forces into the mechanistic world-view appeared to be a triumphant vindication of Newton's foresight. But it was really only the beginning of a story, not the end of one. Subsequent investigations were to show that an electric current - a flow of charge - could produce a magnetic force. This showed that the apparently separate subjects of electricity and magnetism were actually different aspects of a single subject: electromagnetism.

Two of the other books in the Physical World series, Static fields and potentials and Dynamic fields and waves give a thorough discussion of electromagnetism

It was within this unified subject that a new physical concept was to arise, that of a field. The field concept was destined to play an enormously important role in reshaping the physicistís view of the world. It would initially augment the mechanistic world-view, then around 1900, come to rival it, and ultimately, after 1926, play an important part in its downfall.

Figure 1.17s Faraday (1791-1867) Click here for larger image (16.99kb) Faraday, one of the most accomplished experimental researchers of all time Click here to learn more about Faraday

Figure 1.19s Maxwell (1831-1879) Click here for larger image (11.51kb) The first Professor of Experimental Physics in the University of Cambridge Click here to learn more about Maxwell

The field theory of electromagnetism was mainly the creation of two men, Michael Faraday and James Clerk Maxwell. They are, in a sense, the Galileo and the Newton of field theory.

Figure 1.20 Maxwell's equations, the fundamental laws of electromagnetism. Click here for larger image (4.29kb)

The problem that led Faraday to introduce the concept of a field was an old one; how could one body exert a force on another that was separated from it by empty space? Scientists and philosophers of earlier ages had devised essentially two possible answers.

The simpler but less appealing possibility was that it just happened - that action at a distance was part of the fundamental reality of Nature and, as such, needed no further explanation.

The other possibility was that the notion of empty space was a delusion, that the Universe was actually full of matter, albeit a very subtle and unusual form of matter, and that force was transmitted from one place to another by direct contact between parts of that matter. There were several different proposals concerning the exact nature of this 'subtle matter' that could transmit forces, but it was generally referred to as ether, and theories that made use of it were therefore called ether theories.
Continue on to Electromagnetism and fields part 3 of 4