Question 1

The classical free-electron theory of metals

Accepted Answer

A)  correctly predicts the resistivity of a conductor but fails to predict the correct temperature dependence of the resistivity. 
B)  correctly predicts both the resistivity of a conductor and its temperature dependence. 
C)  incorrectly predicts the resistivity of a conductor but correctly predicts its temperature dependence. 
D)  incorrectly predicts both the resistivity of a conductor and its temperature dependence. 
E)  correctly predicts which materials are conductors, insulators, or semiconductors. 
A)  correctly predicts the resistivity of a conductor but fails to predict the correct temperature dependence of the resistivity. 
B)  correctly predicts both the resistivity of a conductor and its temperature dependence. 
C)  incorrectly predicts the resistivity of a conductor but correctly predicts its temperature dependence. 
D)  incorrectly predicts both the resistivity of a conductor and its temperature dependence. 
E)  correctly predicts which materials are conductors, insulators, or semiconductors.

Question 2

Molecules in a gas

Accepted Answer

A)  have little influence on one another. 
B)  have little influence on one another except during their frequent but brief collisions. 
C)  are close together and exert forces on one another that are comparable to the forces that bind atoms into molecules. 
D)  form temporary short-range bonds that continually break and re-form due to the thermal kinetic energy of the molecules. 
E)  are always arranged in a crystalline structure. 
A)  have little influence on one another. 
B)  have little influence on one another except during their frequent but brief collisions. 
C)  are close together and exert forces on one another that are comparable to the forces that bind atoms into molecules. 
D)  form temporary short-range bonds that continually break and re-form due to the thermal kinetic energy of the molecules. 
E)  are always arranged in a crystalline structure.

Question 3

Use the following to answer the next question.
 
-The Fermi energy in three dimensions at T = 0 is given by
EF = 0.365 eV · nm2 (N/V)2/3
The Fermi energy for potassium is approximately

Accepted Answer

A)  11.7 eV 
B)  3.24 eV 
C)  5.53 eV 
D)  2.11 eV 
E)  9.46 eV 
A)  11.7 eV 
B)  3.24 eV 
C)  5.53 eV 
D)  2.11 eV 
E)  9.46 eV

Question 4

The symbol for a pnp transistor is

Accepted Answer

A)  1 
B)  2 
C)  3 
D)  4 
E)  5 
A)  1 
B)  2 
C)  3 
D)  4 
E)  5

Question 5

The free-electron model of metals gives a good account of electrical conduction if

Accepted Answer

A)  the classical mean speed vav is replaced by the Fermi speed uF. 
B)  the collisions between electrons and the lattice ions are interpreted in terms of the scattering of electron waves. 
C)  the collisions between electrons and the lattice ions are interpreted in terms of the scattering of hard spheres. 
D)  the classical mean speed vav is retained in the model and the collisions between electrons and the lattice ions are interpreted in terms of the scattering of electron waves. 
E)  the classical mean speed vav is replaced by the Fermi speed uF and the collisions between electrons and the lattice ions are interpreted in terms of the scattering of electron waves. 
A)  the classical mean speed vav is replaced by the Fermi speed uF. 
B)  the collisions between electrons and the lattice ions are interpreted in terms of the scattering of electron waves. 
C)  the collisions between electrons and the lattice ions are interpreted in terms of the scattering of hard spheres. 
D)  the classical mean speed vav is retained in the model and the collisions between electrons and the lattice ions are interpreted in terms of the scattering of electron waves. 
E)  the classical mean speed vav is replaced by the Fermi speed uF and the collisions between electrons and the lattice ions are interpreted in terms of the scattering of electron waves.

Question 6

A metal is a good conductor because the valence energy band for electrons is

Accepted Answer

A)  empty. 
B)  completely full. 
C)  full, but there is only a small gap to a higher empty band. 
D)  partly full. 
E)  None of these is correct. 
A)  empty. 
B)  completely full. 
C)  full, but there is only a small gap to a higher empty band. 
D)  partly full. 
E)  None of these is correct.

Question 7

If the atoms are treated as solid spheres, the fraction of volume occupied by the atoms in a face-centered-cubic unit cell is

Accepted Answer

A)  0.45 
B)  0.52 
C)  0.65  
D)  0.68 
E)  0.74  
A)  0.45 
B)  0.52 
C)  0.65  
D)  0.68 
E)  0.74

Question 8

Silicon is one of the Group IV semiconductors and has an energy gap of 1.12 eV. Generally only metals have highly shiny surface, yet as shown in the figure, silicon appears to reflect like a metal. This is because

Accepted Answer

A)  silicon is a good semiconductor with a well defined energy gap. 
B)  visible light has energies in the range 2-3 eV which is much larger than the energy gap allowing electrons to be promoted from the valence band to the conduction band. 
C)  the surface of silicon is smooth making it reflect like a metal. 
D)  silicon can be grown in very high purity. It is the impurities that make a semiconductor dull looking. 
E)  None of these is correct. 
A)  silicon is a good semiconductor with a well defined energy gap. 
B)  visible light has energies in the range 2-3 eV which is much larger than the energy gap allowing electrons to be promoted from the valence band to the conduction band. 
C)  the surface of silicon is smooth making it reflect like a metal. 
D)  silicon can be grown in very high purity. It is the impurities that make a semiconductor dull looking. 
E)  None of these is correct.

Question 9

Use the following to answer the next question.
 
-The speed of a conduction electron whose energy is equal to the Fermi energy EF for aluminum is

Accepted Answer

A)  1.57* 106 m/s 
B)  1.84 * 106 m/s 
C)  1.21 * 106 m/s 
D)  2.03 * 106 m/s 
E)  3.14 * 106 m/s 
A)  1.57* 106 m/s 
B)  1.84 * 106 m/s 
C)  1.21 * 106 m/s 
D)  2.03 * 106 m/s 
E)  3.14 * 106 m/s

Question 10

Copper has a mass density of 8.93 g/cm3 and its molar mass is 63.55 g. If each copper atom contributes one free electron, the carrier density is

Accepted Answer

A)  8.46 * 1028 m-3 
B)  3.12*1028 m-3 
C)  4.15 *1028 m-3 
D)  6.48 *1028 m-3 
E)  None of these is correct. 
A)  8.46 * 1028 m-3 
B)  3.12*1028 m-3 
C)  4.15 *1028 m-3 
D)  6.48 *1028 m-3 
E)  None of these is correct.

Question 11

The classical theory of conduction

Accepted Answer

A)  fails because electrons are not classical particles. 
B)  does not take into account the scattering of electron waves by a lattice. 
C)  fails to correctly describe the collision of an electron with a lattice ion. 
D)  predicts a Maxwell-Boltzmann-like distribution of electron velocities. 
E)  is described by all of these. 
A)  fails because electrons are not classical particles. 
B)  does not take into account the scattering of electron waves by a lattice. 
C)  fails to correctly describe the collision of an electron with a lattice ion. 
D)  predicts a Maxwell-Boltzmann-like distribution of electron velocities. 
E)  is described by all of these.

Question 12

If the energy levels of a Fermi gas is given by En = nE1, the total energy of seven fermions in the ground state is

Accepted Answer

A)  7E1 
B)  9E1 
C)  11E1 
D)  14E1 
E)  16E1 
A)  7E1 
B)  9E1 
C)  11E1 
D)  14E1 
E)  16E1

Question 13

Use the following to answer the next question.
 
-The Fermi energy in three dimensions at T = 0 is given by
EF = 0.365 eV · nm2 (N/V)2/3
The Fermi energy for sodium is approximately

Accepted Answer

A)  11.7 eV 
B)  3.24 eV 
C)  5.53 eV 
D)  2.11 eV 
E)  9.46 eV 
A)  11.7 eV 
B)  3.24 eV 
C)  5.53 eV 
D)  2.11 eV 
E)  9.46 eV

Question 14

The classical microscopic model of electric conduction

Accepted Answer

A)  successfully predicts Ohm's law. 
B)  relates the resistivity of conductors to the mean speed and the mean free path of the free electrons within the conductor. 
C)  fails to correctly predict the measured values of resistivity. 
D)  fails to account for the distinction between insulators, semiconductors, and conductors. 
E)  is described by all of these statements. 
A)  successfully predicts Ohm's law. 
B)  relates the resistivity of conductors to the mean speed and the mean free path of the free electrons within the conductor. 
C)  fails to correctly predict the measured values of resistivity. 
D)  fails to account for the distinction between insulators, semiconductors, and conductors. 
E)  is described by all of these statements.

Question 15

KF has a face-centered-cubic lattice structure and the equilibrium spacing between the K+ and F- ions is 0.269 nm. It has a dissociation energy of 498 kJ/mol. The constant n in the empirical potential energy, Urep = A/rn, is

Accepted Answer

A)  2.2 
B)  4.3 
C)  5.8 
D)  6.9 
E)  8.7  
A)  2.2 
B)  4.3 
C)  5.8 
D)  6.9 
E)  8.7

Question 16

The frequency of the current observed at a Josephson junction is 976 MHz. The voltage applied to the junction to produce this current was

Accepted Answer

A)  202 µV 
B)  1.43 V 
C)  1.43 µV 
D)  2.02 µV 
E)  1.28 µV 
A)  202 µV 
B)  1.43 V 
C)  1.43 µV 
D)  2.02 µV 
E)  1.28 µV

Question 17

The probability that an energy state in magnesium 0.2 eV below the Fermi energy is occupied at T = 300 K is

Accepted Answer

A)  5.52% 
B)  20.6% 
C)  47.1% 
D)  83.9% 
E)  99.9% 
A)  5.52% 
B)  20.6% 
C)  47.1% 
D)  83.9% 
E)  99.9%

Question 18

The probability that an energy state in magnesium 0.2 eV above the Fermi energy is occupied at T = 300 K is

Accepted Answer

A)  0.0365% 
B)  0.0404% 
C)  0.0438% 
D)  0.0457% 
E)  0.0496% 
A)  0.0365% 
B)  0.0404% 
C)  0.0438% 
D)  0.0457% 
E)  0.0496%

Question 19

A Josephson junction is a junction of

Accepted Answer

A)  two ordinary conductors. 
B)  an ordinary conductor and a superconductor. 
C)  an insulator and a superconductor. 
D)  two superconductors. 
E)  an insulator and an ordinary conductor. 
A)  two ordinary conductors. 
B)  an ordinary conductor and a superconductor. 
C)  an insulator and a superconductor. 
D)  two superconductors. 
E)  an insulator and an ordinary conductor.

Question 20

Forward biasing of a pn junction

Accepted Answer

A)  lowers the potential across a junction and increases the diffusion of holes and electrons. 
B)  raises the potential across a junction and increases the diffusion of holes and electrons. 
C)  raises the potential across a junction and decreases the diffusion of holes and electrons. 
D)  lowers the potential across a junction and decreases the diffusion of holes and electrons. 
E)  None of these is correct. 
A)  lowers the potential across a junction and increases the diffusion of holes and electrons. 
B)  raises the potential across a junction and increases the diffusion of holes and electrons. 
C)  raises the potential across a junction and decreases the diffusion of holes and electrons. 
D)  lowers the potential across a junction and decreases the diffusion of holes and electrons. 
E)  None of these is correct.

Exam 18: Solids and the Theory of Conduction

The classical free-electron theory of metals

Molecules in a gas

Use the following to answer the next question. -The Fermi energy in three dimensions at T = 0 is given by EF = 0.365 eV · nm2 (N/V)2/3 The Fermi energy for potassium is approximately

The symbol for a pnp transistor is

The free-electron model of metals gives a good account of electrical conduction if

A metal is a good conductor because the valence energy band for electrons is

If the atoms are treated as solid spheres, the fraction of volume occupied by the atoms in a face-centered-cubic unit cell is

Silicon is one of the Group IV semiconductors and has an energy gap of 1.12 eV. Generally only metals have highly shiny surface, yet as shown in the figure, silicon appears to reflect like a metal. This is because

Use the following to answer the next question. -The speed of a conduction electron whose energy is equal to the Fermi energy EF for aluminum is

Copper has a mass density of 8.93 g/cm3 and its molar mass is 63.55 g. If each copper atom contributes one free electron, the carrier density is

The classical theory of conduction

If the energy levels of a Fermi gas is given by En = nE1, the total energy of seven fermions in the ground state is

Use the following to answer the next question. -The Fermi energy in three dimensions at T = 0 is given by EF = 0.365 eV · nm2 (N/V)2/3 The Fermi energy for sodium is approximately

The classical microscopic model of electric conduction

KF has a face-centered-cubic lattice structure and the equilibrium spacing between the K+ and F- ions is 0.269 nm. It has a dissociation energy of 498 kJ/mol. The constant n in the empirical potential energy, Urep = A/rn, is

The frequency of the current observed at a Josephson junction is 976 MHz. The voltage applied to the junction to produce this current was

The probability that an energy state in magnesium 0.2 eV below the Fermi energy is occupied at T = 300 K is

The probability that an energy state in magnesium 0.2 eV above the Fermi energy is occupied at T = 300 K is

A Josephson junction is a junction of

Forward biasing of a pn junction

The Electric Field I: Discrete Charge Distributions

The Electric Field II: Continuous Charge Distributions

Electric Potential

Capacitance

Electric Current and Direct-Current Circuits

The Magnetic Field

Sources of the Magnetic Field

Magnetic Induction

Alternating-Current Circuits

Maxwells Equations and Electromagnetic Waves

Properties of Light

Optical Images

Interference and Diffraction

Wave Particle Duality and Quantum Physics

Applications of the Schrodinger Equation

Atoms

Molecules

Relativity

Nuclear Physics

Elementary Particles and the Beginning of the Universe

Filters

Use the following to answer the next question. -The Fermi energy in three dimensions at T = 0 is given by E_F = 0.365 eV · nm² (N/V)^2/3 The Fermi energy for potassium is approximately

Use the following to answer the next question. -The speed of a conduction electron whose energy is equal to the Fermi energy E_F for aluminum is

Copper has a mass density of 8.93 g/cm³ and its molar mass is 63.55 g. If each copper atom contributes one free electron, the carrier density is

If the energy levels of a Fermi gas is given by E_n = nE₁, the total energy of seven fermions in the ground state is

Use the following to answer the next question. -The Fermi energy in three dimensions at T = 0 is given by E_F = 0.365 eV · nm² (N/V)^2/3 The Fermi energy for sodium is approximately

KF has a face-centered-cubic lattice structure and the equilibrium spacing between the K⁺ and F^- ions is 0.269 nm. It has a dissociation energy of 498 kJ/mol. The constant n in the empirical potential energy, U_rep = A/rⁿ, is