Question

Which of the following is/are true among the following?

• A. The electron in valance band does not contribute to conducting current whereas electron from conduction band contribute in conducting current.
• B. The electron in valance band contributes to conducting current whereas electron from conduction band does not contribute in conducting current.
• C. The electrons from both the conducting and valance band contribute to conduct electricity
• D. The electrons from neither conducting band nor valance band contribute to conduct electricity

Answer 1

The correct option is A The electron in valance band does not contribute to conducting current whereas electron from conduction band contribute in conducting current.

Electricity or electric current is contributed only from electrons in the conduction band. Whereas holes in the valence band contribute to hole current or conventional current.
For example: In case of an insulator, the valence band is filled with electrons whereas conduction band is empty. So, the insulator has zero conductivity unless electrons shift from valence to conduction band when the temperature rises.