The electricity deals with phenomena which are related to electric charges and forces. These phenomena in be categorized into the electrostatics and the electrodynamics. In electrostatics the fundamental relations are treated which are caused by immobile electric charges and no time dependence is present. It is characteristic in electrostatics that there exists two kinds of charges named as positive and negative. If the sign of the charge of two objects is the same, there is a repulsive force while the force is attractive for opposite signs. In electrostatic instead the movement of charges or the time dependence of electric fields are treated. The fundamental equations in electrodynamics were derived by James Clarke Maxwell who expressed the relations between electric and magnetic fields which also allows the description of electromagnetic waves.During the development of the quantum theory in the twentieth century the electodynamics was extended since electromagnetic waves could not be treated in the classical way anymore but they also were described by a movement of a particle named phonon.