Which one of the following statements is conect with regard to the material of electrical insulators ?

Electrical insulators are materials that impede or prevent the flow of electric current [1]. Unlike conductors, where electrons move freely, the electrons in insulators are typically tightly bound to their parent atoms and do not have significant mobility. This lack of free electron mobility is due to the electronic band structure; in insulators, the valence band is completely full and there is a large energy gap (band gap) that electrons must cross to reach the conduction band. Consequently, while insulators do contain electrons (refuting option 1), these electrons do not flow easily through the material even when an external electric field is applied. While some insulators like ceramics or diamond are crystalline, many others like rubber and plastic are amorphous, making option 3 incorrect as a general rule [1]. Option 4 is incorrect as materials are generally electrically neutral unless specifically charged.

Sources

1. [1] Science-Class VII . NCERT(Revised ed 2025) > Chapter 3: Electricity: Circuits and their Components > 3.2 A Simple Electrical Circuit > p. 36