This video lecture from Group IIIA and Group IVA Elements (F.Sc. second year Chemistry) covers semi conductors. It covers their definition, material types, intrinsic and extrinsic semi conductors, passage of current through intrinsic semi conductors and addition of impurities (doping) to increase the number of electron hole pairs and hence conductance. 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.