Tag: semiconductors

Quizzes (4) Questions (79)

Questions Related to semiconductors

Multiple choice physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

Among the following, the wrong statement in the case of semiconductor is:

  1. Resistivity is in between that of a conductor and insulator.

  2. Temperature coefficient of resistance is negative.

  3. Doping increases conductivity.

  4. At absolute zero temperature, it behaves like a conductor.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

For semiconductor, as the temperature coefficient of resistance is negative, at absolute zero temperature, it behaves like an insulator.

Multiple choice physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

What is the resistivity of a pure semiconductor at absolute zero ?

  1. Zero

  2. Infinity

  3. Same as that of conductors at room temperature

  4. Same as that of insulators at room temperature
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The electricity conductivity of a semiconductor at $0 K$ is zero. hence resistivity (= 1/electrical conductivity) is infinity.

Multiple choice physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

Bands in solids are formed due to a group of closely spaced ________ .

  1. conductor bands

  2. valance bands

  3. energy levels

  4. solid bands
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Closely space energy levels combine to form an energy band in solids. This is because, the outer orbit of an atom in solids, are common to several neighboring atoms. Therefore, energy levels corresponding to outer orbit electrons spread up to form a band of energy called energy band.

Multiple choice physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

The energy gap in glass at room temperature is :

  1. greater than that in a semiconductor

  2. less than that in a good conductor

  3. greater than that in a good conductor

  4. both (A) and (C) are true
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Glass is an insulator. The energy gap of an insulator is $\sim 6 eV$. Whereas for conductors, the energy gap is $\sim 0 eV$.
for semiconductors, energy gap $\sim 3 eV$.
So energy gap for glass is greater in conductors or a semiconductor.

Multiple choice physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

A pure semiconductor at absolute zero has :

  1. absence of electrons in the conduction band

  2. all the electrons occupying the valence band

  3. large ${E} _{g}$ value

  4. all of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

At absolute zero, a pure semiconductor behaves as an insulator. Electrons have insufficient thermal energy to jump the gap, so the conduction band is empty, the valence band is full, and the band gap energy is characteristic of the material.

Multiple choice physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

The band structure determines the _________ behaviour of a solid.

  1. chemical

  2. electrical

  3. mechanical

  4. molecular
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The band structure, i.e. valence band, conduction band and forbidden energy band (Eg) tells on the basis of the energy difference between valence and conduction band, that whether the given solid is a metal, insulator or a semiconductor. If the two bands overlap, then the solid is a conductor, i.e, it has high electrical conductivity. If Eg $\sim 6$ eV; then it is an insulator and has minimum electrical conductivity otherwise if Eg $\sim 3$ eV, it is a semiconductor whose electrical conductivity lies between conductor and insulator.