The correct answer is option 3: Dielectrics. Dielectrics are non-conducting materials that can be polarized by an electric field. When an electric field is applied to a dielectric material, the positive and negative charges within the material are displaced in opposite directions, causing an internal separation of charges. This separation of charges creates an electric dipole moment in the material.
Dielectrics are commonly used in capacitors and insulation materials because of their ability to store electrical energy. When a dielectric is placed between the plates of a capacitor, it reduces the electric field within the capacitor, increasing its capacitance. This allows the capacitor to store a larger amount of electrical charge.
Semi-conductors, on the other hand, are materials that have conductivity between that of a conductor and an insulator. They can be controlled to exhibit positive or negative conductivity depending on the presence of impurities or external electric fields. Superconductors, on the other hand, exhibit zero electrical resistance at very low temperatures. Resistive conductors refer to materials that have a high electrical resistance.