Solid State Physics MCQs Question and Answer in Engineering Physics

21

The temperature dependence of the electrical conductivity σ of two intrinsic semiconductors A and B is shown in the figure. If E_A and E_B are the band gaps of A and B respectively, which one of the following is true?
Solid State Physics mcq question image

A) E_A > E_B B) E_A < E_B C) E_A = E_B D) E_A and E_B both depend on temperature

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Answer & Solution

Answer: Option A

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22

In a one-dimensional Kronig-Penny model, the total number of possible wave functions is equal to

A) twice the number of unit cells B) number of unit cells C) half the number of unit cells D) independent of the number of unit cells

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Answer & Solution

Answer: Option B

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23

The plot of inverse magnetic susceptibility $$\frac{1}{\chi }$$ versus temperature T of an antiferromagnetic sample corresponds to

A)

B)

C)

D)

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Answer & Solution

Answer: Option B

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24

An n-type semiconductor has an electron concentration of 3 × 10²⁰ m^-3. If the electron drift velocity is 100 m/s in an electric field of 200 V/m, the conductivity (in $${\Omega ^{ - 1}}$$ m^-1) of this material is

A) 24 B) 36 C) 48 D) 96

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Answer & Solution

Answer: Option B

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25

For a NaCI crystal, the cell-edge a = 0.563 nm. The smallest angle at which Bragg reflection can occur corresponds to a set of planes whose indices are

A) 1 0 0 B) 1 1 0 C) 1 1 1 D) 2 0 0

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Answer & Solution

Answer: Option A

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26

An intrinsic semiconductor with mass of a hole m_h, and mass of an electron m_e is at a finite temperature T. If the top of the valence band energy is E_v and the bottom of the conduction band energy is E_c, the Fermi energy of the semiconductor is

A) $${E_F} = \left( {\frac{{{E_v} + {E_c}}}{2}} \right) - \frac{3}{4}{k_B}T\ln \left( {\frac{{{m_h}}}{{{m_e}}}} \right)$$ B) $${E_F} = \left( {\frac{{{k_B}T}}{2}} \right) + \frac{3}{4}\left( {{E_v} + {E_c}} \right)\ln \left( {\frac{{{m_h}}}{{{m_e}}}} \right)$$ C) $${E_F} = \left( {\frac{{{E_v} + {E_c}}}{2}} \right) + \frac{3}{4}{k_B}T\ln \left( {\frac{{{m_h}}}{{{m_e}}}} \right)$$ D) $${E_F} = \left( {\frac{{{k_B}T}}{2}} \right) - \frac{3}{4}\left( {{E_v} + {E_c}} \right)\ln \left( {\frac{{{m_h}}}{{{m_e}}}} \right)$$

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Answer & Solution

Answer: Option C

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27

A superconducting ring is cooled in the presence of a magnetic field below its critical temperature (T_c). The total magnetic flux that passes through the ring is

A) zero B) $$n\frac{h}{{2e}}$$ C) $$\frac{{nh}}{{4\pi e}}$$ D) $$\frac{{n{e^2}}}{{hc}}$$

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Answer & Solution

Answer: Option A

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28

For a conventional superconductor, which of the following statements is not true?

A) Specific heat is discontinuous at transition temperature T_c B) The resistivity falls sharply at T_c C) It is diamagnetic below T_c D) It is paramagnetic below T_c

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Answer & Solution

Answer: Option D

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29

Consider X-ray diffraction from a crystal with a face centred cubic (fcc) lattice. The lattice plane for which there is no diffraction peak is

A) (2, 1, 2) B) (1, 1, 1) C) (2, 0, 0) D) (3, 1, 1)

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Answer: Option D

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30

The order of magnitude of the energy gap of a typical superconductor is

A) 1 MeV B) 1 keV C) 1 eV D) 1 meV

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Answer & Solution

Answer: Option C

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