Correct Answer – 4
Intrinsic semiconductors are basically insulators where the energy gap between adjacent energy band is sufficiently small for thermal energy to be able to promote a small number of electrons from the full valence band to the empty conduction band .Both the promoted electrons in the conduction band and the unpaired electrons left in the in the valence band can conduct electricity.
The conductivity of semiconductors increase with temperature because the number of electrons promoted to the conduction band increase as temperatures increases.
Both n-type and p-type semiconductors bands to the impurity bands or vica versa.
A superconductor is a material that loses all electrical resistance below a characteristic temperature called the super conducting transition temperature `T_(C)` Below its `T_(C)` a super conductor becomes a perfect conductor, and an elecrtric current once started flows indefinetly without loss of energy ,for example the electrical resistance of `Hg` falls to zero at its superconducting transiiton temperature `T_(C)=4.2K` Above `T_(C)` mercury is a metallic conductor,Its resistance increases (conductivity decreases) with increasing temperature increase (conductivity decrease) with decreasing temperature .Below `T_(C)` mercury is a superconductor.