Solid State Physics II - SS3 Physics Past Questions and Answers - page 2

Conductors are materials that allow the flow of electric charge easily. They have high electrical conductivity and low resistance. Metals are examples of conductors.

Insulators have very low electrical conductivity and high resistance. They have a wide band gap between the valence band and the conduction band, which means that electrons are not able to move easily from the valence band to the conduction band. Examples of insulators include rubber, glass, and plastics.

A diode is a two-terminal electronic component that conducts electric current in only one direction. It has a p-n junction, which is formed by doping one side of a semiconductor crystal with impurities that create a surplus of electrons (n-type) and the other side with impurities that create a deficiency of electrons (p-type).

A transistor is a three-terminal electronic device that can amplify or switch electronic signals. It consists of a sandwich of p-type and n-type semiconducting materials, with two junctions between them. The three terminals are called the emitter, base, and collector.