The physics of electromagnetic phenomena is governed by the electromagnetic interaction, which includes both electricity and magnetism. It is based on a quantity called charge, of which there are two varieties–positive or negative. Of course, not all particles are charged in the first place, and so-called “neutral” particles couldn’t care less about the electromagnetic interaction.
Like charges repel, and opposite charges attract. The discovery of the law of attraction or repulsion between two charged particles dates back to the French physicist Charles Coulomb. In 1785, he deduced that the force (F) between two charges (q1 and q2) separated by a distance (r) is given by . Here, the value k (like Newton’s G) is just a constant of proportionality. This compact formula, with striking similarities to Newton’s gravitational law, indicates that the electromagnetic interaction also has infinite range.
The theoretical unification of electricity and magnetism was carried out by James Clerk Maxwell. His very elegant equations describe how electric and magnetic fields are generated and altered by each other and by static or moving charges (the latter now known as electric currents).
The electromagnetic force is the interaction responsible for most of the phenomena encountered in daily life. Ordinary matter takes its form as a result of electromagnetic forces between individual atoms and molecules, themselves formed by the electromagnetic interaction between protons and electrons. Also, the manifestation of friction, air resistance, drag, tension, and Scotch tape are all ultimately due to electromagnetic forces at the atomic level.
We saw how Schroedinger’s equation can be applied to determine the structure of atoms. To do so, we had to introduce a potential energy function. The origin of this function was none other than the electromagnetic interaction. As a result, this is the fundamental interaction that binds electrons into orbitals around atomic nuclei to form atoms. This also governs the processes involved in chemistry, which arise from interactions between the electrons of neighboring atoms in molecules.
Thus, within the atoms, where charged electrons and protons interact directly with one another, the electromagnetic force dominates. The electromagnetic interaction is also among the strongest–even when compared to the aptly-named strong force (more below). The theoretical implications of electromagnetism, in particular the establishment of the speed of light, led to the development of special relativity by Albert Einstein in 1905.
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