question_answer

The energy gap between the valence and conduction bands of an insulator is about

A)  0.1 eV

B)  1.0 eV

C)  5.0 eV                 

D)         zero

Correct Answer: C

Solution :

An insulator has its valence band filled with electrons and its conduction band is empty. The energy gap is large approximately\[5.0\text{ }eV\], so it is not possible for ordinary process to provide enough energy for valence electrons to break out of their valence band and jump into the conduction band where they might carry electric current.