Question

The free electron density is more in
a) Conductors
b) Insulators
c) Semiconductors
d) Electrolytes

Answer 1

Hint: To answer the above question, we first need to know what the above each of the substances mean. First we will define each of the above substances and discuss the presence of free electrons in each of the substances. Further accordingly we will choose the correct answer as to which of the substances have maximum free electron density.

Complete answer:
To begin with let us first discuss the conductors. Conductors are substances that allow the current to flow through it easily when a potential difference is applied to it. The conduction band and the valence band overlap each other in case of conductors. Therefore electrons easily move from the valence to the conduction band. As a result, conductors have many free electrons in the conduction band which constitute the current in the closed circuit.
Insulators are substances which do not allow the flow of current through it. This is because the distance between the conduction and the valence band is huge. As a result, no free electrons are available in the conduction band which can allow the flow of current.
Semiconductors are substances which conduct flow of current at high temperatures. This is because as the temperature increases the distance between the valence and the conduction band is reduced. As a result, the electrons jump to the conduction band thereby conducting electricity.
Electrolytes are substances that produce an electrically conducting solution when dissolved in a polar solvent, such as water. This dissolution results in the formation of ions in the solution which constitute the flow of current.
Hence from the above information we can conclude that conductors have more electron density than any other substances.

Hence the correct answer of the above question is option a.

Note:
Electron density is responsible for the flow of current in the given circuit. At high temperatures the conductors i.e. metals do not conduct electricity that effectively than semiconductors. This does not imply that at higher temperatures semiconductors have more free electron density than conductors. It is just that the electrons in conductors at higher temperature possess energy and move randomly colliding with other electrons and ions of the metal. Therefore the flow of current is reduced.