What is the correct sequence of conductivity when arranged in ascending order?

Electrical conductivity is a measure of a material's ability to allow the flow of electric current. Materials are classified into three categories based on this property: insulators, semiconductors, and metals. Insulators, such as rubber and glass, have extremely low conductivity (and high resistivity) because they lack free charge carriers [2]. Semiconductors, like silicon and germanium, possess intermediate conductivity levels that lie between those of insulators and conductors [1]. Metals (conductors) exhibit the highest conductivity due to the presence of a large number of free electrons that facilitate current flow. Therefore, when arranged in ascending order (from lowest to highest conductivity), the correct sequence is insulators, followed by semiconductors, and finally metals. This classification is fundamentally based on the energy band gap between the valence and conduction bands.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > Activity 11.3 > p. 179