61. What is electrodynamics?

In mechanics, different types of motion of macroscopic bodies under the action of certain forces are studied, in molecular physics - the chaotic motion of atoms and molecules, which forms the basis of heat processes. The nature of forces and their origin are not studied either in mechanics or in molecular physics.

In electrodynamics first of all study electromagnetic interactions of bodies, i.e. forces having electromagnetic nature.

Among the four types of interactions - gravitational, electromagnetic, nuclear and weak - it is electromagnetic forces that take first place in the breadth and diversity of phenomena in nature. In everyday life and technology, with some exceptions (for example, gravity to the Earth), we meet constantly only with different types of electromagnetic interactions. These are the forces of elasticity, friction, strength of our muscles.
(Weak interactions mainly determine the transformations of elementary particles.)

Electromagnetic interactions allow you to see the book you are reading, because light is one of the forms of electromagnetic interactions. Life itself is unthinkable without these forces. Living creatures and even humans, as shown by the flights of astronauts, are able to stay in a state of weightlessness for a long time, when the forces of gravity are not shown. But if the action of electromagnetic forces stopped for a moment, life would immediately disappear.

In the interaction of particles in the most compact systems of nature - in the atomic nuclei and the interaction of cosmic bodies (by light), electromagnetic forces play an exceptional role, while nuclear, weak and gravitational interactions are essential only in either very small or cosmic scales. The structure of the atomic shell, the bonding of atoms into molecules (chemical forces) and the formation of pieces of matter are determined exclusively by electromagnetic forces. It is difficult, almost impossible to specify phenomena that would not be related to the action of electromagnetic forces.

The creation of science - electrodynamics led to a long chain of random discoveries and systematic research, ranging from the discovery of the strange ability of amber rubbed on silk, attract lightweight objects and ending with the guessing of the great English scientist James Clerk Maxwell (1831-1879) on the generation of magnetic fields by variable electric fields. Only after the creation of electrodynamics, in the second half of XIX century, began a wide practical use of electromagnetic phenomena. The invention of radio is one of the first and most important applications of the principles of the new theory. At development of electrodynamics for the first time purely scientific researches preceded technical applications. If a steam machine was built long before the theory of heat processes, it was possible to design an electric motor or a radio receiver only after discovering and studying the laws of electrodynamics.

Our task is to learn the basic laws of electromagnetic interactions.