This video lecture from Group IIIA and Group IVA Elements (F.Sc. second year Chemistry) is a continuation of the last lecture on semi conductors. Semi conductors may be doped using trivalent or pentavalent impurities yielding P or N type material respectively. These materials together enhance conductance and form diodes and transistors of type PNP and NPN. Addition of heat energy (increasing temperature) and light energy makes it easier to release more electrons from atoms, creating more electron hole pairs and hence increasing conductance. A numerical demonstration makes it easier to understand the concept of conductance in semiconductors quantitatively. Find more e-learning material and educational video lectures in Urdu at maktab.pk. These videos are free to use for promotional and commercial purpose by keeping the credits to Maktab.