MSE HW 10
1. Equation Ne = N0exp(-Eg/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
A solid characterized by a partially filled valence band is a(n) __________________. A. Conductor B. Semiconductor C. Insulator
A. Conductor
A solid with Ez = 0 is a(n) __________________. A. Conductor B. Semiconductor C. Insulator
A. Conductor
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
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 = N0exp(-Eg/2kT) B. Ne = N0exp(Eg/2kT) C. Ne = N0exp(-(E^2)g/2kT) D. None of the above
A. Ne = N0exp(-Eg/2kT)
As temperature increase, the mean time between collisions of electrons in a conductor ______________. A. Reduces B. Increases C. Stays the same
A. Reduces
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.
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
A material with an energy band gap of 1 eV will be a semiconductor. This statement is ______. A. True B. False
A. True
A material with an energy band gap of 5 eV will be an insulator. This statement is ______. A. True B. False
A. True
Addition of B (boron) to Si is an example of p-type of conductor. This statement is _____. A. True B. False
A. True
Addition of P to Si creates n-type of conductor. This statement is ______________. A. True B. False
A. True
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
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
Both electrons and holes can transport charge. This statement is _____. A. True B. False
A. True
Carbon in the form of diamond is an electrical insulator. This statement is _______. A. True B. False
A. True
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
In superconducting materials, resistivity approaches zero. This statement is _______. A. True B. False
A. True
Metal oxides, many ceramics, and most polymers are electrical insulator. This statement is _______. A. True B. False
A. True
Most common semiconductor materials such Si and Ge have covalent bonds. This statement is ________. A. True B. False
A. True
Some polymers are electrical conductors. Polyaniline is an example of electrically conducting polymer. This statement is _______. A. True B. False
A. True
Thermoelectric effect can be used to measure the temperature. This statement is _______. A. True B. False
A. True
In most materials, resistivity increases with increase in temperature. This statement is ______. A. True B. False
A. True and B. False (This is true in metals and other conductors, but not in semiconductors.)
Based on the Fermi-Dirac distribution function: which one of the following statements 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
Carbon in the form of graphite is an electrical insulator. This statement is _______. A. True B. False
B. False
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
The number of mobile electrons per atom for aluminum (Z = 13) is ______________. A. 1 B. 2 C. 3 D. 4
C. 3
Which material is not a band gap material? A. Silicon B. Diamond C. Copper D. Aluminum doped silicon
C. Copper
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
A band gap material with a large band gap is likely to be a(n) _________________. A. Conductor B. Semiconductor C. Insulator
C. Insulator
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
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
Carbon in the form of carbon nanotube is ________. A. Conductor B. Semiconductor C. Insulator D. Conductor or semiconductor
D. Conductor or semiconductor
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(-Eg/kT) B. σ = σ0 exp(Eg/kT) C. σ = σ0 exp(Eg/kT)^2 D. None of the above
D. None of the above
Which of the following has the highest electrical conductivity? A. Polyethylene B. Window glass C. P (phosphorus) doped Si D. Silver
D. Silver
Which one of the following solids has the highest electrical conductivity? A. Aluminum B. Copper C. Gold D. Silver
D. Silver
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
