Question 1

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 2

For a pure semiconductor the Fermi level is:

Accepted Answer

A) in the conduction band 
B) well above the conduction band 
C) in the valence band 
D) well below the valence band 
E) near the center of the gap between the valence and conduction bands 
A) in the conduction band 
B) well above the conduction band 
C) in the valence band 
D) well below the valence band 
E) near the center of the gap between the valence and conduction bands

Question 3

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 4

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$\degree$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 5

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

Accepted Answer

A) increases the drift current in the depletion zone 
B) increases the diffusion current in the depletion zone 
C) decreases the drift current on the p side outside the depletion zone 
D) decreases the drift current on the n side outside the depletion zone 
E) does not change the current anywhere 
A) increases the drift current in the depletion zone 
B) increases the diffusion current in the depletion zone 
C) decreases the drift current on the p side outside the depletion zone 
D) decreases the drift current on the n side outside the depletion zone 
E) does not change the current anywhere

Question 6

Which of the following is NOT true when a back bias is applied to a p-n junction?

Accepted Answer

A) Electrons flow from the p to the n side 
B) Holes flow from the p to the n side 
C) The electric field in the depletion zone increases 
D) The potential difference across the depletion zone increases 
E) The depletion zone narrows 
A) Electrons flow from the p to the n side 
B) Holes flow from the p to the n side 
C) The electric field in the depletion zone increases 
D) The potential difference across the depletion zone increases 
E) The depletion zone narrows

Question 7

Donor 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 8

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 9

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

Exam 41: Conduction of Electricity in Solids

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

For a pure semiconductor the Fermi level is:

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:

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 °\degree° C.The material is most likely:

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

Which of the following is NOT true when a back bias is applied to a p-n junction?

Donor atoms introduced into a pure semiconductor at room temperature:

A hole refers to:

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

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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 $\degree$ C.The material is most likely: