Deck 23: Conduction of Electricity in Solids

Question 1

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

A) n = 10²⁹ m^-3, 11ef175a_747e_fecd_8934_9df8412bf74a_TB7453_11 = 10^-8 $\Omega$ . m, $\infty$ = +10^-3 K^-1
B) n = 10²⁸ m^-3, 11ef175a_747e_fecd_8934_9df8412bf74a_TB7453_11 = 10^-9 $\Omega$ . m, $\infty$ = -10^-3 K^-1
C) n = 10²⁸ m^-3, 11ef175a_747e_fecd_8934_9df8412bf74a_TB7453_11 = 10^-9 $\Omega$ . m, $\infty$ = +10^-3 K^-1
D) n = 10¹⁵ m^-3, 11ef175a_747e_fecd_8934_9df8412bf74a_TB7453_11 = 10³ $\Omega$ . m, $\infty$ = -10^-2 K^-1
E) n = 10²² m^-3, 11ef175a_747e_fecd_8934_9df8412bf74a_TB7453_11= 10^-7 $\Omega$ .m, $\infty$ = +10^-3 K^-1

Answer 1

n = 10¹⁵ m^-3, = 10³ $\Omega$ . m, $\infty$ = -10^-2 K^-1

Question 2

The density of states for a metal depends primarily on:

A) the temperature
B) the energy associated with the state
C) the density of the metal
D) the volume of the sample
E) none of these

Answer 2

the energy associated with the state

Question 3

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

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

Answer 3

0 and 1

Question 4

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

A)
B)
C)
D)
E)

Question 5

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

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

Question 6

Ther Fermi energy of a metal depends primarily on:

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

Question 7

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

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

A hole refers to:

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

For a pure semiconductor the Fermi level is:

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 10

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

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

Question 11

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

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

Question 12

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

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