MSE2001 HW10
21. Equation Ne = N0exp(- E_g/(2kT )) applies to _______ A. A material with a band gap B. A material with no band gap C. Both A and B D. Neither A or B
A. A material with a band gap
33. A solid characterized by a partially filled valence band is a(n) __________________. A. Conductor B. Semiconductor C. Insulator
A. Conductor
34. A solid with E_g = 0 is a(n) __________________. A. Conductor B. Semiconductor C. Insulator
A. Conductor
27. The mean time between collisions of electrons in a conductor will be ______by lattice defects. Thus the mobility of electrons will be _______. A. Decreased, decreased B. Increased, increased C. Decreased, increased D. Increased, decreased
A. Decreased, decreased
11. For a band gap material, number of electrons in the conduction band at a given temperature is given by which of the following equation? (symbols have their usual meaning) A. Ne = N0*exp(-E_g/(2kT )) B. Ne = N0*exp(E_g/(2kT )) C. Ne = N0*exp(-(E_g)^2/(2kT )) D. None of the above
A. Ne = N0*exp(-E_g/(2kT ))
26. As temperature increase, the mean time between collisions of electrons in a conductor ______________. A. Reduces B. Increases C. Stays the same
A. Reduces
32. In a solid, which energy band has the highest energy? A. The conduction band. B. The forbidden band. C. The valence band. D. The core band.
A. The conduction band.
31. As temperature increases, which one of the following statements is INCORRECT? A. The energy of an energy band increases B. The charge mobility decreases C. The drift velocity of electrons decreases D. As the temperature increases, the probability of an electron to occupy higher energy levels is increased.
A. The energy of an energy band increases
1. Addition of two P (phosphorus) atoms to 1 million Si (silicon) atoms increases the conductivity by a factor of 5 million. This statement is _____. A. True B. False
A. True
10. A material with an energy band gap of 5 eV will be an insulator. This statement is ______. A. True B. False
A. True
13. Most common semiconductor materials such Si and Ge have covalent bonds. This statement is ________. A. True B. False
A. True
14. Carbon in the form of diamond is an electrical insulator. This statement is _______. A. True B. False
A. True
17. Metal oxides, many ceramics, and most polymers are electrical insulator. This statement is _______. A. True B. False
A. True
18. Some polymers are electrical conductors. Polyaniline is an example of electrically conducting polymer. This statement is _______. A. True B. False
A. True
19. In superconducting materials, resistivity approaches zero. This statement is _______. A. True B. False
A. True
2. Addition of P to Si creates n-type of conductor. This statement is ______________. A. True B. False
A. True
20. Thermoelectric effect can be used to measure the temperature. This statement is _______. A. True B. False
A. True
23. Band gap of a semiconducting material can be determined by measuring its conductivity as a function of temperature. This statement is _______. A. True B. False
A. True
28. Both electrons and holes can transport charge. This statement is _____. A. True B. False
A. True
3. Addition of B (boron) to Si is an example of p-type of conductor. This statement is _____. A. True B. False
A. True
7. Energy band gap refers to magnitude of the forbidden energy range between the valence and conduction bands. This statement is ______________. A. True B. False
A. True
9. A material with an energy band gap of 1 eV will be a semiconductor. This statement is ______. A. True B. False
A. True
12. In most materials, resistivity increases with increase in temperature. This statement is ______. [ρ(T)= ρ_0 (1+ α_e ∆T),symbols have their usual meaning] A. True B. False
A. True This is true in metals and other conductors, but not in semiconductors.
7. Based on the Fermi-Dirac distribution function: f(E)= 1/(exp[((E-E_(f ) ))/kT]+1) , which one of the following statement is correct? A. At E = Ef, f(E) = 1 at any temperature B. At E > Ef, f(E) = 0 at 0 K C. At E < Ef, f(E) = 0 at 0 K D. None of the above
B. At E > Ef, f(E) = 0 at 0 K
15. Carbon in the form of graphite is an electrical insulator. This statement is _______. A. True B. False
B. False
37. The critical energy gap to distinguish between a semiconductor and an insulator is approximately _________________. A. 1.0 eV B. 0.1 eV C. 2.5 eV D. 0.25 eV
C. 2.5 eV
25. The number of mobile electrons per atom for aluminum (Z = 13) is ______________. A. 1 B. 2 C. 3 D. 4
C. 3
36. Which material is not a band gap material? A. Silicon B. Diamond C. Copper D. Aluminum doped silicon
C. Copper
30. Based on the following energy band diagrams, which one of the following statements is INCORRECT? A. Diagram a represents conductor B. Diagram b represents semiconductor C. Diagram c represents semiconductor D. Diagram c represents insulator
C. Diagram c represents semiconductor
35. A band gap material with a large band gap is likely to be a(n) _________________. A. Conductor B. Semiconductor C. Insulator
C. Insulator
6. Which of the following is the correct unit of electrical conductivity? A. Ampere B. Ohms per meter C. Siemens per meter D. None of the above
C. Siemens per meter
29. Based on the following electron distribution in Figures A and B, which one of the following statements is correct? A. The number of charge carriers in Figure A is greater than in Figure B B. The number of charge carriers in Figure A is less than in Figure B C. The number of charge carriers in Figure A is same as in Figure B D. None of the above
C. The number of charge carriers in Figure A is same as in Figure B (Both electrons and holes can transport charge)
16. Carbon in the form of carbon nanotube is ________. A. Conductor B. Semiconductor C. Insulator D. Conductor or semiconductor
D. Conductor or semiconductor
22. Which one of the following equation is the correct equation of the conductivity of a semiconductor as a function of temperature? A. σ = σ0*exp(-E_g/(kT )) B. σ = σ0*exp(E_g/(kT ) ) C. σ = σ0*exp(-E_g/(kT ))^2 D. None of the above
D. None of the above
24. Which one of the following solids has the highest electrical conductivity? A. Aluminum B. Copper C. Gold D. Silver
D. Silver
5. Which of the following has the highest electrical conductivity? A. Polyethylene B. Window glass C. P (phosphorus) doped Si D. Silver
D. Silver
4. For electrical conduction, which of the following is correct? (symbols have their usual meaning) A. V = IR B. ρ = (A )/L R C. σ= 1/ρ D. σ=Nqμ E. All of the above
E. All of the above
