This set of Engineering Physics Multiple Choice Questions & Answers (MCQs) focuses on “Properties of Semiconductors”.
1. How does a semiconductor behave at absolute zero?
d) Protection device
Explanation: A semiconductor is a solid which has the energy band similar to that of the insulator. It acts as an insulator at absolute zero.
2. Semiconductor acts as an insulator in the presence of impurities.
Explanation: When the temperature is raised or when an impurity is added, their conductivity increases. Conductivity is inversely proportional to temperature.
3. How is the resistance of semiconductor classified?
a) High resistance
b) Positive temperature co-efficient
c) Negative temperature co-efficient
d) Low resistance
Explanation: Semiconductors have negative temperature co-efficient. The reason for this is, when the temperature is increased, a large number of charge carriers are produced due to the breaking of covalent bonds and hence these electrons move freely and gives rise to conductivity.
4. What are the charge carriers in semiconductors?
a) Electrons and holes
Explanation: In conductors, electrons are charge carriers. But in semiconductors, both electrons and holes are charge carriers and will take part in conduction.
5. Which of the following is known as indirect band gap semiconductors?
Explanation: The elemental semiconductor is made up of a single element from the fourth column elements such as Germanium. Here recombination takes place takes place via traps. It is called indirect band gap semiconductors.
6. Which column elements are combined to make compound semiconductors?
a) First and fourth
b) Fifth and sixth
c) Second and fourth
d) Third and fifth
Explanation: The compound semiconductors are made by combining the third and fifth column elements. Such as GaAs are made by combining third and fifth column elements.
7. Compound semiconductors are also known as direct band gap semiconductors.
Explanation: In compound semiconductors, recombination takes place directly and its energy difference is emitted in the form of photons in the visible or infrared range. Hence the compound semiconductors are also known as direct band gap semiconductors.
8. How is charge carriers produced in intrinsic semiconductors?
a) By pure atoms
b) By electrons
c) By impure atoms
d) By holes
Explanation: Impure semiconductors in which the charge carriers are produced due to impurity atoms are called extrinsic semiconductors. They are obtained by doping an intrinsic semiconductor with impurity atoms.
9. What type of material is obtained when an intrinsic semiconductor is doped with pentavalent impurity?
a) N-type semiconductor
b) Extrinsic semiconductor
c) P-type semiconductor
Explanation: N-type semiconductor is obtained by doping an intrinsic semiconductor with pentavalent impurity atoms.
10. What type of material is obtained when an intrinsic semiconductor is doped with trivalent impurity?
a) Extrinsic semiconductor
c) N-type semiconductor
d) P-type semiconductor
Explanation: P-type semiconductor is obtained by doping an intrinsic semiconductor with trivalent impurity.
Sanfoundry Global Education & Learning Series – Engineering Physics.
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