Question

In insulators __________ . (C.B is conduction band and V.B is valence band)
(A). V.B. is partially filled with electrons
(B). C.B. is partially filled with electrons
(C). C.B. is empty and V.B. is filled with electrons
(D). C.B. is filled with electrons and V.B. is empty

Answer 1

Hint: As we know conductors are the substance that conducts heat and electricity, semiconductors are the material that may act as conductors, as well as insulators depending upon different conditions. To solve this problem we will define the insulator, energy band, valence band and the conduction band, then we will see the given options.

Complete step-by-step solution -
Insulators - insulators are those materials which do now allow the current to pass through it For examples wood, plastics, mica etc.
Energy band- in any material there are a large number of atoms. And these atoms have electrons in various orbits which have various levels of energy that are called energy bands.
valence band- the outermost electron called valence electron is at the outer most orbit of the atom and can be removed and becomes free from this orbit by supplying energy.
Conduction band- when electrons are free to move then only there can be flow of current and when the electrons gets this level of energy then it is said that it gets in the conduction band.
And in case of insulators there is a huge gap in between the energy of valence band and conduction band so the electrons cannot reach to the conduction band even after getting some energy and thus the conduction band of insulators are empty.

Hence the correct option is C.

Note: In case of conductor conduction band and valence band coincide with each other and allow the flow of electrons i.e. current whereas for semiconductors there is small gap between the conduction band and the valence band and if the electron has sufficient energy it will pass the band gap, thus conduct and if the energy provided is not enough for conduction then semiconductor behave as insulator; while insulators does not allow current to flow through it.