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## Physics- James Clerk Maxwell

Many physicists feel that James Clerk Maxwell should be mentioned in the same breath as the two greats in the field, Newton, who lived before, and Einstein, who lived after him. Born in Edinburgh in 1831, he was already a professor of physics in Aberdeen at the age of 25 and five years later at King's College in London. After another five years, living at home, he began his major work, a treatise on electricity and magnetism.

A forerunner in this field is Michael Faraday, the man with the famous cage which makes you safer in a closed car during a thunderstorm than under a tree. But actually much more important for the development of the theory of electricity is his discovery of magnetic induction, without which there would not be a single electric motor today, for example. Consequently, after the first battery from Volta, the first dynamo came from Faraday.

It is interesting to see the relations, this is what happened expressly from Einstein to Maxwell and from Maxwell to Faraday. The latter here as an excerpt from the Brockhaus, 21st edition, under the appropriate keyword:

'[…] he conceives of all space as a field of force in which the lines of force are generally curved; starting from one body, they spread out in all directions, their direction being deflected by other bodies'.

In contrast to Faraday, Maxwell mastered mathematics and wrote his original 20 equations, later simplified to 4, for what is now referred to as the electric and magnetic fields. For the former, a sphere is to be provided with a specific electrical charge. So we are looking for the force emanating from the sphere on another, assumedly smaller one, at a given distance. In addition, Maxwell's equations take into account the directions of the electric field and existing magnetic fields, as well as their magnitudes. There are two transformable forms of the equations, one for single point calculations, the other for areas.

In order to explain this in more detail, we will tie in with the well-known school experiment with iron arrow filings. Of course, this is only for illustrative purposes, also because it offers a two-dimensional representation. In reality, one has to imagine magnetic fields on the one hand and electrical fields between a positive and a negative charge on the other hand spatially. Magnetic fields only affect certain elements such as iron, electric fields only affect charges in the field. You want to know something about their behavior. Actually, one takes a space out of the electric field which can be reduced quasi arbitrarily and looks at the behavior of so-called test charges there.

A force acts on these charges. It is not enough to calculate this in absolute terms, because two forces that act perpendicularly on each other, for example, cannot be added together. The benefit of Maxwell's equations lies in the fact that the forces that act on test charges at any locations in the electric field are mathematically broken down into the X, Y and Z directions and only then, in relation to a small space, and only then to have determined, related to a small space, what positive minus negative charge is there and where it is moving. Without these basics, how do you intend to determine, for example, the windings of an electric motor and the currents to be controlled with them?

This close look at electric fields leads directly to the theory of the electromagnetic waves, which propagate at the speed of light. Maxwell concluded that light was related to electromagnetism, hitherto considered separate in physics. Incidentally, the basic invention for radio technology appears here. However, Maxwell took a medium as the basis for wave propagation and called it light-ether. The increasing contradictions to the wave character of light finally led to Einstein's special theory of relativity.

This is the reason why Einstein is said to have said that he does not stand on the shoulders of Newton so much as on those of Maxwell. Incidentally, the invention of benzene by Faraday and one of the most important foundations of the kinetic theory of gases by Maxwell are of importance for automotive engineering. From him comes e.g. the insight that the temperature of gas molecules manifests itself in the form of oscillations. Oh, yes, then, in addition to knowledge in the field of chemistry, he also came up with the theory of three colors, i.e. that each color is made up of the primary colors red, green and blue.

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