This chapter covers electric phenomena in dielectric materialsDielectric material. When an electric fieldElectric field is applied to a dielectric materialDielectric material, the electrons are slightly displaced along the direction opposite to the electric fieldElectric field, even though they are bonded by nuclei. This phenomenon is electric polarizationElectric polarization. As a result, electric dipolesElectric dipole are produced and polarization chargePolarization charge appears. Thus, the electric fieldElectric field is produced by true electric chargesTrue electric charge and also by polarization chargesPolarization charge in dielectric materialsDielectric material. We newly define the electric flux densityElectric flux density, which describes only the electric fieldElectric field produced by the true electric chargeTrue electric charge. Electric phenomena are generally described in terms of the electric fieldElectric field and the electric flux densityElectric flux density. The refraction of the electric fieldElectric field at an interface between different dielectric materialsDielectric material is also treated.