Question 1

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 2

A certain material has a resistivity of 7.8 *10-8  $\Omega$ .m at room temperature and it 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 3

In a pure metal the collisions that are characterized by the mean free time  $ \tau $ in the expression for the resistivity are chiefly between:

Accepted Answer

A)  electrons and other electrons 
B)  electrons with energy about equal to the Fermi energy and atoms 
C)  all electrons and atoms 
D)  electrons with energy much less than the Fermi energy and atoms 
E)  atoms and other atoms 
A)  electrons and other electrons 
B)  electrons with energy about equal to the Fermi energy and atoms 
C)  all electrons and atoms 
D)  electrons with energy much less than the Fermi energy and atoms 
E)  atoms and other atoms

Question 4

At T = 0 K the probability that a state 0.50 eV below 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 5

For an unbiased p-n junction, the energy at the bottom of the conduction band on the n side is:

Accepted Answer

A)  higher than the energy at the bottom of the conduction band on the p side 
B)  lower than the energy at bottom of the conduction band on the p side 
C)  lower than energy at the top of the valence band on the n side 
D)  lower than energy at the top of the valence band on the p side 
E)  the same as the energy at the bottom of the conduction band on the p side 
A)  higher than the energy at the bottom of the conduction band on the p side 
B)  lower than the energy at bottom of the conduction band on the p side 
C)  lower than energy at the top of the valence band on the n side 
D)  lower than energy at the top of the valence band on the p side 
E)  the same as the energy at the bottom of the conduction band on the p side

Question 6

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 7

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 8

When a forward bias is applied to a p-n junction the concentration of electrons on the p side:

Accepted Answer

A)  increases slightly 
B)  increases dramatically 
C)  decreases slightly 
D)  decreases dramatically 
E)  does not change 
A)  increases slightly 
B)  increases dramatically 
C)  decreases slightly 
D)  decreases dramatically 
E)  does not change

Exam 41: Conduction of Electricity in Solids

Donor atoms introduced into a pure semiconductor at room temperature:

A certain material has a resistivity of 7.8 *10-8 Ω\OmegaΩ .m at room temperature and it increases as the temperature is raised by 100 °\degree° C. The material is most likely:

In a pure metal the collisions that are characterized by the mean free time τ \tau τ in the expression for the resistivity are chiefly between:

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

For an unbiased p-n junction, the energy at the bottom of the conduction band on the n side is:

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

A pure semiconductor at room temperature has:

When a forward bias is applied to a p-n junction the concentration of electrons on the p side:

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A certain material has a resistivity of 7.8 *10^-⁸ $\Omega$ .m at room temperature and it increases as the temperature is raised by 100 $\degree$ C. The material is most likely:

In a pure metal the collisions that are characterized by the mean free time $\tau$ in the expression for the resistivity are chiefly between: