Classical (nonquantum) electromagnetic theory, in which the quantum law with its constant, h, is ignored, deals with electric charges and currents and their interactions. The theory is based on an experiment that is secure within its range of application to coils, capacitors, oscillating currents, and eventually radio and optical waves. We can describe the repulsion and attraction of particles using the same laws that apply to the leaves of an electroscope; quantum mechanics is needed to predict the behavior of the particles under those forces. Without going into details of the experiments by which the existence of electric charge, q(= 1.6× 10−19 coulomb; C) was demonstrated, we shall enumerate the basic laws of stationary electric charges, called the electrostatics; the source of the static electric ﬁeld is a stationary charge. The fundamental property of this charge is its existence in two varieties, positive (+) and negative (−). The charged particles are created in pairs with equal and opposite charge. The total electric charge in an isolated system does not change.