Question On Thermal Properties with Answers

Practice Question On Thermal Properties with Answers.

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Question On Thermal Properties with Answers


Q1. In two dimensions two metals A and B, have the number density of free electrons in the ratio n:m = 1:2. The ratio of their Fermi energies is

  • (A) 2:3 
  • (B) 1:2 
  • (C) 1:8 
  • (D) 1:4

Q2. Fermi energy of a certain metal M is 5 eV. A second metal M’ has an electron density which is 6% higher than that of M. Assuming that the free electron theory is valid for both the metals, the Fermi energy of M’ is closest to

  • (A) 5.6 eV 
  • (B) 4.8 eV 
  • (C) 5.2 eV 
  • (D) 4.4 eV

Q3. The Dulong-Petit law fails near room temperature (300 K) for many light clements (such as boron and beryllium) because their Debye temperature is

  • (A) >> 300 K 
  • (B) ~ 300 K 
  • (C) << 300 K 
  • (D) 0 K

Q4. What is the contribution of the condition electrons in the molar entropy of a metal with electronic coefficient of specific heat ?

  • (A) γT 
  • (B) γT
  • (C) γT
  • (D) γT4

Q5. According to Dulong-Petit’s law, the specific heat of a solid

  • (A) is proportional to the temperature 
  • (B) depends on square of temperature 
  • (C) does not depend on temperature 
  • (D) is inversely proportional to temperature

Q6. The Debye temperature of a metal is 450 K. Its Debye frequency in Hz is of the order of

  • (A) 1011 
  • (B) 1016 
  • (C) 1013 
  • (D) 1026

Q7. Debye temperatures of copper and gold are 340K and 170K, respectively. At room temperature, if the specific heat for copper is 1.5 kJmol^-1K^-1, the specific heat for gold is about:

  • (A) 1.2 kJmol-1K-1 
  • (B) 0.19 kJmol-1K-1 
  • (C) 1.9 kJmol-1K-1 
  • (D) 12 kJmol-1K-1

Q8. The Fermi energy ε in metals depends on the number density n of mobile electrons, which may be thought of as a free Fermi gas. If n of one metal is larger by a factor of 1000 compared to another, then in comparison, its Fermi energy is

  • (A) 1000 times larger 
  • (B) smaller by a factor of 1/100 
  • (C) 100 times larger 
  • (D) 10 times larger

Q9. Flow of electron is affected by which of the following:

  • (A) thermal vibration
  • (B) only impurity atom
  • (C) only crystal defects
  • (D) only all of (a), (b) & (c)

Q10. Fermi energy level for intrinsic semiconductors lies:

  • (A) at the middle of the band gap 
  • (B) close to the conduction band 
  • (C) close to valence band 
  • inside valence band

Q11. The Fermi energy of silver is 5.51 electron volt. The average energy of the free electrons in silver at 0 °K is given by

  • (A) 0.864 eV 
  • (B) 0.864 eV 
  • (C) 4.205 eV 
  • (D) 3.306 eV

Q12. Which of the following statements concerning the electrical conductivities at room temperature of apure copper sample and a pure silicon sample is NOT true ?

  • (A) If the temperature of the copper sample is increased, its conductivity will decrease 
  • (B) If the temperature of the silicon sample is increased, its conductivity will increase 
  • (C) The addition of an impurity in the copper sample always decreases its conductivity 
  • (D) The addition of an impurity in the silicon always decreases its conductivity

Q13. In the Kronig-Penney model, electrons are assumed to be moving in

  • (A) one-dimensional square well potential 
  • (B) one-dimensional square well periodic potential 
  • (C) a periodic harmonic potential 
  • (D) three-dimensional coulomb potential

Q14. The general expression for the Fermi energy of a metal at 0°K (if n is the number of free electrons/m3) is

  • (A) 3.65 x 10-19 n2/3 eV 
  • (B) 3.65 x 1019 n2 eV 
  • (C) 3.65 x 1019 n1/3 eV 
  • (D) 3.65 x 1019 n3/2 eV

Q15. Fermi level represents the energy level with probability of its occupation of

  • (A) 0% 
  • (B) 25% 
  • (C) 50% 
  • (D) 100%

NOTE:- If you need anything else like e-books, video lectures, syllabus, etc. regarding your Preparation / Examination then do 📌 mention it in the Comment Section below. 
NOTE:- If you need anything else like e-books, video lectures, syllabus, etc. regarding your Preparation / Examination then do 📌 mention it in the Comment Section below. 

Answer Key (if you find any answer wrong, feel free to Correct us)

01.(B)06.(C)11.(C)
02.(C)07.(D)12.(D)
03.(A)08.(C)13.(B)
04.(A)09.(D)14.(A)
05.(C)10.(A)15.(C)

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