Insulator

Insulator Points : Insulator, Definition The materials, in which conduction and -valance bands are separated by a wide energy gap (= 15eV) are called insulators (also referred to as dielectric materials). A wide energy gap means that a large amount of energy is required, to free the electrons, by moving them from the valance band into the condition band. Since at room temperature, the valance electrons of an insulator do not have enough energy to jump into the conduction band, therefore insulators do not have an ability to conduct current. Thus insulators have very high resistivity (or extremely low conductivity) at room temperatures. However, if the temperature is raised some of the valence electrons may acquire energy and jump into the conduction band. It causes the resistivity of insulators to decrease. Therefore the insulators have negative-temperature coefficient of resistance.