Question 1

The occupancy probability for a state with energy equal to the Fermi energy is:

Accepted Answer

A)  0 
B)  0.5 
C)  1 
D)  1.5 
E)  2 
A)  0 
B)  0.5 
C)  1 
D)  1.5 
E)  2 B

Question 2

At room temperature kT is about 0.0259 eV. The probability that a state 0.50 eV below the Fermi level is unoccupied at room temperature is:

Accepted Answer

A)  1 
B)  0.05 
C)  0.025 
D)  5.0 *10-6 
E)  4.1*10-9 
A)  1 
B)  0.05 
C)  0.025 
D)  5.0 *10-6 
E)  4.1*10-9 E

Question 3

A hole refers to:

Accepted Answer

A)  a proton 
B)  a positively charged electron 
C)  an electron which has somehow lost its charge 
D)  a microscopic defect in a solid 
E)  the absence of an electron in an otherwise filled band 
A)  a proton 
B)  a positively charged electron 
C)  an electron which has somehow lost its charge 
D)  a microscopic defect in a solid 
E)  the absence of an electron in an otherwise filled band E

Question 4

For a metal at absolute temperature T, with Fermi energy EF, the occupancy probability is given by:

Accepted Answer

A)    
B)    
C)    
D)    
E)    
A)    
B)    
C)    
D)    
E)

Question 5

A certain material has a resistivity of 7.8 *103  $\Omega$. m at room temperature and it decreases as the temperature is raised by 100$\degree$C. The material is most likely:

Accepted Answer

A)  a metal 
B)  a pure semiconductor 
C)  a heavily doped semiconductor 
D)  an insulator 
E)  none of the above 
A)  a metal 
B)  a pure semiconductor 
C)  a heavily doped semiconductor 
D)  an insulator 
E)  none of the above

Question 6

A given doped semiconductor can be identified as p or n type by:

Accepted Answer

A)  measuring its electrical conductivity 
B)  measuring its magnetic susceptibility 
C)  measuring its coefficient of resistivity 
D)  measuring its heat capacity 
E)  performing a Hall effect experiment 
A)  measuring its electrical conductivity 
B)  measuring its magnetic susceptibility 
C)  measuring its coefficient of resistivity 
D)  measuring its heat capacity 
E)  performing a Hall effect experiment

Question 7

If the density of states is N(E) and the occupancy probability is P(E), then the density of unoccupied states is:

Accepted Answer

A)  N(
E)  + P(
E)  
B)  N(
E) /P(
E)  
C)  N(
E)  - P(
E)  
D)  N(
E) P(
E)  
E)  P(
E) /N(
E)  
A)  N(
E)  + P(
E)  
B)  N(
E) /P(
E)  
C)  N(
E)  - P(
E)  
D)  N(
E) P(
E)  
E)  P(
E) /N(
E)

Question 8

An acceptor replacement atom in silicon might have ______ electrons in its outer shell.

Accepted Answer

A)  3 
B)  4 
C)  5 
D)  6 
E)  7 
A)  3 
B)  4 
C)  5 
D)  6 
E)  7

Question 9

Possible units for the density of states function N(E) are:

Accepted Answer

A)  J/m3 
B)  1/J 
C)  m-3 
D)  J-1.m-3 
E)  kg/m3 
A)  J/m3 
B)  1/J 
C)  m-3 
D)  J-1.m-3 
E)  kg/m3

Question 10

The energy level diagram shown applies to:

Accepted Answer

A)  a conductor 
B)  an insulator 
C)  a semiconductor 
D)  an isolated molecule 
E)  an isolated atom 
A)  a conductor 
B)  an insulator 
C)  a semiconductor 
D)  an isolated molecule 
E)  an isolated atom

Question 11

The energy level diagram shown applies to:

Accepted Answer

A)  a conductor 
B)  an insulator 
C)  a semiconductor 
D)  an isolated molecule 
E)  an isolated atom 
A)  a conductor 
B)  an insulator 
C)  a semiconductor 
D)  an isolated molecule 
E)  an isolated atom

Question 12

"LED" stands for:

Accepted Answer

A)  Less Energy Donated 
B)  Light Energy Degrader 
C)  Luminescent Energy Developer 
D)  Laser Energy Detonator 
E)  none of the above 
A)  Less Energy Donated 
B)  Light Energy Degrader 
C)  Luminescent Energy Developer 
D)  Laser Energy Detonator 
E)  none of the above

Question 13

Switch S is closed to apply a potential difference V across a p-n junction as shown. Relative to the energy levels of the n-type material, with the switch open, the electron levels of the p-type material are:

Accepted Answer

A)  unchanged 
B)  lowered by the amount e-Ve/kT 
C)  lowered by the amount Ve 
D)  raised by the amount e-Ve/kT 
E)  raised by the amount Ve 
A)  unchanged 
B)  lowered by the amount e-Ve/kT 
C)  lowered by the amount Ve 
D)  raised by the amount e-Ve/kT 
E)  raised by the amount Ve

Question 14

The gap between the valence and conduction bands of a certain semiconductor is 0.85eV. When this semiconductor is used to form a light emitting diode, the wavelength of the light emitted:

Accepted Answer

A)  is in a range above 1.5*10-6 m 
B)  is in a range below 1.5 *10-6 m 
C)  is always 1.5 *10-6 m 
D)  is in a range centered on 1.5 *10-6 m 
E)  has nothing to do with the gap 
A)  is in a range above 1.5*10-6 m 
B)  is in a range below 1.5 *10-6 m 
C)  is always 1.5 *10-6 m 
D)  is in a range centered on 1.5 *10-6 m 
E)  has nothing to do with the gap

Question 15

A certain metal has 5.3 *1029 conduction electrons/m3 and an electrical resistivity of 1.9* 10-9 $\Omega$ m.The average time between collisions of electrons with atoms in the metal is:

Accepted Answer

A)  5.6 * 10-33 s 
B)  1.3*10-31 s 
C)  9.9 * 10-22 s 
D)  4.6 * 10-15 s 
E)  3.5*10-14 s 
A)  5.6 * 10-33 s 
B)  1.3*10-31 s 
C)  9.9 * 10-22 s 
D)  4.6 * 10-15 s 
E)  3.5*10-14 s

Question 16

A donor replacement atom in silicon might have ______ electrons in its outer shell.

Accepted Answer

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

Question 17

At T = 0 K the probability that a state 0.50 eV above the Fermi level is occupied is:

Accepted Answer

A)  0 
B)  5.0*10-9 
C)  5.0 * 10-6 
D)  5.0 * 10-3 
E)  1 
A)  0 
B)  5.0*10-9 
C)  5.0 * 10-6 
D)  5.0 * 10-3 
E)  1

Question 18

Acceptor atoms introduced into a pure semiconductor at room temperature:

Accepted Answer

A)  increase the number of electrons in the conduction band 
B)  increase the number of holes in the valence band 
C)  lower the Fermi level 
D)  increase the electrical resistivity 
E)  none of the above 
A)  increase the number of electrons in the conduction band 
B)  increase the number of holes in the valence band 
C)  lower the Fermi level 
D)  increase the electrical resistivity 
E)  none of the above

Question 19

The speed of an electron with energy equal to the Fermi energy for copper is on ther order of:

Accepted Answer

A)  106 m/s 
B)  10-6 m/s 
C)  10 m/s 
D)  10-1 m/s 
E)  109 m/s 
A)  106 m/s 
B)  10-6 m/s 
C)  10 m/s 
D)  10-1 m/s 
E)  109 m/s

Question 20

The number density n of conductions electrons, the resistivity $\rho$, and the temperature coefficient of resistivity $\infty$ are given below for five materials. Which is a semiconductor?

Accepted Answer

A)  n = 1029 m-3, $\rho$ = 10-8  $\Omega$ . m, $\infty$ = +10-3 K-1 
B)  n = 1028 m-3, $\rho$= 10-9  $\Omega$ . m, $\infty$ = -10-3 K-1 
C)  n = 1028 m-3, $\rho$= 10-9 $\Omega$ . m, $\infty$ = +10-3 K-1 
D)  n = 1015 m-3, $\rho$ = 103  $\Omega$ . m,$\infty$ = -10-2 K-1 
E)  n = 1022 m-3, $\rho$= 10-7 $\Omega$ . m, $\infty$= +10-3 K-1 
A)  n = 1029 m-3, $\rho$ = 10-8  $\Omega$ . m, $\infty$ = +10-3 K-1 
B)  n = 1028 m-3, $\rho$= 10-9  $\Omega$ . m, $\infty$ = -10-3 K-1 
C)  n = 1028 m-3, $\rho$= 10-9 $\Omega$ . m, $\infty$ = +10-3 K-1 
D)  n = 1015 m-3, $\rho$ = 103  $\Omega$ . m,$\infty$ = -10-2 K-1 
E)  n = 1022 m-3, $\rho$= 10-7 $\Omega$ . m, $\infty$= +10-3 K-1

Exam 41: Conduction of Electricity in Solids

The occupancy probability for a state with energy equal to the Fermi energy is:

At room temperature kT is about 0.0259 eV. The probability that a state 0.50 eV below the Fermi level is unoccupied at room temperature is:

A hole refers to:

For a metal at absolute temperature T, with Fermi energy EF, the occupancy probability is given by:

A certain material has a resistivity of 7.8 *103 Ω\OmegaΩ . m at room temperature and it decreases as the temperature is raised by 100 °\degree° C. The material is most likely:

A given doped semiconductor can be identified as p or n type by:

If the density of states is N(E) and the occupancy probability is P(E), then the density of unoccupied states is:

An acceptor replacement atom in silicon might have ______ electrons in its outer shell.

Possible units for the density of states function N(E) are:

The energy level diagram shown applies to:

The energy level diagram shown applies to:

"LED" stands for:

Switch S is closed to apply a potential difference V across a p-n junction as shown. Relative to the energy levels of the n-type material, with the switch open, the electron levels of the p-type material are:

The gap between the valence and conduction bands of a certain semiconductor is 0.85eV. When this semiconductor is used to form a light emitting diode, the wavelength of the light emitted:

A certain metal has 5.3 *1029 conduction electrons/m3 and an electrical resistivity of 1.9* 10-9 Ω\OmegaΩ m.The average time between collisions of electrons with atoms in the metal is:

A donor replacement atom in silicon might have ______ electrons in its outer shell.

At T = 0 K the probability that a state 0.50 eV above the Fermi level is occupied is:

Acceptor atoms introduced into a pure semiconductor at room temperature:

The speed of an electron with energy equal to the Fermi energy for copper is on ther order of:

The number density n of conductions electrons, the resistivity ρ\rhoρ , and the temperature coefficient of resistivity ∞\infty∞ are given below for five materials. Which is a semiconductor?

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For a metal at absolute temperature T, with Fermi energy E_F, the occupancy probability is given by:

A certain material has a resistivity of 7.8 *10³ $\Omega$ . m at room temperature and it decreases as the temperature is raised by 100 $\degree$ C. The material is most likely:

A certain metal has 5.3 10²⁹ conduction electrons/m³ and an electrical resistivity of 1.9 10^-⁹ $\Omega$ m.The average time between collisions of electrons with atoms in the metal is:

The number density n of conductions electrons, the resistivity $\rho$ , and the temperature coefficient of resistivity $\infty$ are given below for five materials. Which is a semiconductor?