5.1 Introduction5.2 Classical free electron theory of metals5.3 Relaxation time, mean free path, mean collision time and drift velocity5.4 Fermi-Dirac distribution5.5 Quantum free electron theory of electrical conduction5.6 Sources of electrical resistance5.7 Band theory of solids5.8 Bloch theorem5.9 Origin of energy bands formation in solids5.10 Velocity and effective mass of an electron5.11 Distinction between metals, semiconductors and insulatorsFormulaeSolved ProblemsMultiple–choice QuestionsAnswersReview Questions