Semiconductors | MCQs

Explanation

A diode allows current to flow in only one direction — from anode (positive) to cathode (negative).

It acts as a one-way valve for electric current, conducting only when forward-biased (positive to anode, negative to cathode).

Explanation

Explanation

Good conductors of electricity:-

gold,

silver,

copper,

aluminum,

and graphite.

***

Bad conductors of electricity:-

plastic,

rubber,

glass,

air,

wood,

charcoal,

and diamond.

Explanation

 The temperature coefficient of resistance indicates how the resistance of a material changes with temperature.

In semiconductors, as temperature increases, more charge carriers (electrons and holes) become available, so resistance decreases.

Therefore, the temperature coefficient is negative.

Explanation

In a pure (intrinsic) semiconductor:

• The number of electrons in the conduction band is equal to the number of holes in the valence band.

• As a result, the Fermi level lies midway between the conduction band and the valence band.

• This midpoint represents the energy level at which the probability of finding an electron is 50% at absolute zero.

This is a key difference from doped (extrinsic) semiconductors, where the Fermi level shifts depending on the type of doping (n-type or p-type).

Explanation

The energy gap (also called band gap) is the energy difference between the valence band (where electrons are bound) and the conduction band (where electrons are free to move).

• In conductors, the band gap is zero or overlaps.

• In semiconductors, the band gap is around 1 eV (e.g., silicon ≈ 1.1 eV).

• In insulators: The band gap is large, typically greater than 3 eV, and often around 5 eV or more.

This large gap in insulators prevents electrons from moving to the conduction band, making them poor conductors of electricity

Explanation

In an intrinsic semiconductor, there are equal numbers of electrons in the conduction band and holes in the valence band

So the Fermi level, which represents the energy level at which the probability of finding an electron is 50%

Lies right in the middle of the band gap between the valence and conduction bands. 

Explanation

In semiconductors, as the temperature increases, more electrons gain enough energy to jump from the valence band to the conduction band.

This increase in free charge carriers results in higher electrical conductivity.

This is opposite to metals, where conductivity decreases with temperature due to increased scattering of electrons.

Explanation

when a donor impurity interacts with a pure crystal, it leads to the formation of an n-type semiconductor.

Concept:

The process of deliberate addition of a desirable impurity to a pure semiconductor so as to increase its conductivity is called doping

The impurity atoms added are called doped. 

Semiconductors doped with the impurity atoms are called extrinsic.

Explanation:

The element whose atom has five valance electrons are called pentavalent impurities e.g As, P, Sb, etc

These impurities are called donor impurities because they donate an extra free electron.

The semiconductor material with the majority carrier as the electron is called an n-type semiconductor