Question 1

The Fermi-Dirac probability function P(E)varies between:

Accepted Answer

A) 0 and 1 
B) 0 and infinity 
C) 1 and infinity 
D) -1 and 1 
E) 0 and EF  
A) 0 and 1 
B) 0 and infinity 
C) 1 and infinity 
D) -1 and 1 
E) 0 and EF  A

Question 2

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)    C

Question 3

The Fermi energy of a metal depends primarily on:

Accepted Answer

A) the temperature 
B) the volume of the sample 
C) the mass density of the metal 
D) the size of the sample 
E) the number density of conduction electrons 
A) the temperature 
B) the volume of the sample 
C) the mass density of the metal 
D) the size of the sample 
E) the number density of conduction electrons E

Question 4

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 5

In a metal at 0 K, the Fermi energy is:

Accepted Answer

A) the highest energy of any electron 
B) the lowest energy of any electron 
C) the mean thermal energy of the electrons 
D) the energy of the top of the valence band 
E) the energy at the bottom of the conduction band 
A) the highest energy of any electron 
B) the lowest energy of any electron 
C) the mean thermal energy of the electrons 
D) the energy of the top of the valence band 
E) the energy at the bottom of the conduction band

Question 6

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) N(
E) (1 − P(
E) ) 
A) N(
E) + P(
E)  
B) N(
E) /P(
E)  
C) N(
E) - P(
E)  
D) N(
E) P(
E)  
E) N(
E) (1 − P(
E) )

Question 7

Magnesium has 8.6 x 1028 conduction electrons per cubic meter.What is the Fermi energy for magnesium?

Accepted Answer

A) 1.8 eV 
B) 7.1 eV 
C) 9.1 eV 
D) 22 eV 
E) 28 eV 
A) 1.8 eV 
B) 7.1 eV 
C) 9.1 eV 
D) 22 eV 
E) 28 eV

Question 8

A certain material has a resistivity of 7.8 *103  $\Omega$.m at room temperature, and its resistivity decreases as the temperature is raised by 100°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 9

The energy gap between the valence and conduction bands of an insulator is of the order:

Accepted Answer

A) 10-19 eV 
B) 0.001 eV 
C) 0.1 eV 
D) 10 eV 
E) 1000 eV 
A) 10-19 eV 
B) 0.001 eV 
C) 0.1 eV 
D) 10 eV 
E) 1000 eV

Question 10

A certain material has a resistivity of 7.8 *103  $\Omega$.m at room temperature, and its resistivity increases as the temperature is raised by 100 ° 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 11

A light emitting diode emits light when:

Accepted Answer

A) electrons are excited from the valence to the conduction band 
B) electrons from the conduction band recombine with holes from the valence band 
C) electrons collide with atoms 
D) electrons are accelerated by the electric field in the depletion region 
E) the junction gets hot 
A) electrons are excited from the valence to the conduction band 
B) electrons from the conduction band recombine with holes from the valence band 
C) electrons collide with atoms 
D) electrons are accelerated by the electric field in the depletion region 
E) the junction gets hot

Question 12

We classify solids electrically according to three basic properties.What are they?

Accepted Answer

A) Conductivity, resistivity, and crystal structure 
B) Resistivity, temperature coefficient of resistivity, and crystal structure 
C) Resistivity, crystal structure, and number density of conduction electrons 
D) Resistivity, temperature coefficient of resistivity, and number density of conduction electrons 
E) Conductivity, temperature coefficient of resistivity, and crystal structure 
A) Conductivity, resistivity, and crystal structure 
B) Resistivity, temperature coefficient of resistivity, and crystal structure 
C) Resistivity, crystal structure, and number density of conduction electrons 
D) Resistivity, temperature coefficient of resistivity, and number density of conduction electrons 
E) Conductivity, temperature coefficient of resistivity, and crystal structure

Question 13

A pure semiconductor at room temperature has:

Accepted Answer

A) more electrons/m3 in its conduction band than holes/m3 in its valence band 
B) more electrons/m3 in its conduction band than a typical metal 
C) more electrons/m3 in its valence band than at T = 0 K 
D) more holes/m3 in its valence band than electrons/m3 in its valence band 
E) none of the above 
A) more electrons/m3 in its conduction band than holes/m3 in its valence band 
B) more electrons/m3 in its conduction band than a typical metal 
C) more electrons/m3 in its valence band than at T = 0 K 
D) more holes/m3 in its valence band than electrons/m3 in its valence band 
E) none of the above

Question 14

"LED" stands for:

Accepted Answer

A) Less Energy Donated 
B) Light Emitting Degrader 
C) Luminescent Energy Diode 
D) Laser Emitting Device 
E) none of the above 
A) Less Energy Donated 
B) Light Emitting Degrader 
C) Luminescent Energy Diode 
D) Laser Emitting Device 
E) none of the above

Question 15

The contact electric field in the depletion region of a p-n junction is produced by:

Accepted Answer

A) electrons in the conduction band alone 
B) holes in the valence band alone 
C) electrons and holes together 
D) charged replacement atoms 
E) an applied bias potential difference 
A) electrons in the conduction band alone 
B) holes in the valence band alone 
C) electrons and holes together 
D) charged replacement atoms 
E) an applied bias potential difference

Question 16

Application of a forward bias to a p-n junction:

Accepted Answer

A) narrows the depletion zone 
B) increases the electric field in the depletion zone 
C) increases the potential difference across the depletion zone 
D) increases the number of donors on the n side 
E) decreases the number of donors on the n side 
A) narrows the depletion zone 
B) increases the electric field in the depletion zone 
C) increases the potential difference across the depletion zone 
D) increases the number of donors on the n side 
E) decreases the number of donors on the n side

Question 17

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

Accepted Answer

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

Question 18

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

Question 19

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

Question 20

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

Exam 41: Conduction of Electricity in Solids

The Fermi-Dirac probability function P(E)varies between:

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

The Fermi energy of a metal depends primarily on:

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:

In a metal at 0 K, the Fermi energy is:

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

Magnesium has 8.6 x 1028 conduction electrons per cubic meter.What is the Fermi energy for magnesium?

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

The energy gap between the valence and conduction bands of an insulator is of the order:

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

A light emitting diode emits light when:

We classify solids electrically according to three basic properties.What are they?

A pure semiconductor at room temperature has:

"LED" stands for:

The contact electric field in the depletion region of a p-n junction is produced by:

Application of a forward bias to a p-n junction:

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

A hole refers to:

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

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

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

Magnesium has 8.6 x 10²⁸ conduction electrons per cubic meter.What is the Fermi energy for magnesium?

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

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