3.3 Electrical Properties of Materials From an electrical point of view, most materials can be classified into three groups; namely: (a) Conductors. (b) Semi-conductors. (c) Insulators. 3.3.1 Conductors According to atomic theory, an electron can escape from the parent atom and move about between the atoms. This is called a "free electron”. Once an electron escapes from an atom, the atom becomes net positively charged. It may then attract a free electron to become a neutral atom again. Metals are characterized by many free electrons. Materials having many free electrons easily allow an electric current to flow through them and are called conductors. Electrons are the electric c...