Chapter 7: Electrical Properties

Question 1

One of the most important electrical characteristics of a solid
material is the ease with which it transmits an electric current.
___ relates the current I—or time rate of charge passage—
to the applied voltage V

Answer 1

Ohm’s law

Question 2

Ohm’s law

Answer 2

V = IR

Question 3

The ___ ρ is
independent of specimen geometry but related to R

Answer 3

electrical resistivity

Question 4

The value of R is influenced by ___, and for many
materials is independent of current.

Answer 4

specimen configuration

Question 5

is used to specify the
electrical character of a material. It is simply the reciprocal of
the resistivity

Answer 5

electrical conductivity σ

Question 6

An ____ results from the motion of electrically
charged particles in response to forces that act on them from
an externally applied electric field. Positively charged particles
are accelerated in the field direction, negatively charged
particles in the direction opposite.

Answer 6

electric current

Question 7

Within most solid materials a current arises from the flow of
electrons, which is termed

Answer 7

electronic conduction

Question 8

for ionic materials a net motion of charged ions is possible that
produces a current; such is termed

Answer 8

ionic conduction

Question 9

filled - highest occupied energy levels

Answer 9

valence band

Question 10

empty - lowest unoccupied energy levels

Answer 10

conduction band

Question 11

Four possible electron band structures for
solid materials

The various possible electron band structures in solid at 0 K

Answer 11

-empty band, band gap empty states, filled states
-empty band, filled band
-empty conduction band, band gap, filled valence band
-empty conduction band, band gap, filled valence band

Question 12

The electron band structure found in metals such as copper, in which there are available electron states above and adjacent to filled states, in the same band

Answer 12

empty band, band gap, empty states, filled states

Question 13

The electron band structure of metals such as magnesium, wherein there is an overlap of filled and empty outer bands

Answer 13

empty band, filled band

Question 14

The electron band structure characteristic of insulators; the filled valence band is separated from the empty conduction band by a relatively large band gap (>2 eV)

Answer 14

empty conduction band, band gap, filled valence band

Question 15

• (conductors)
• thermal energy puts many electrons into a higher energy state

Answer 15

metals

Question 15

The electron band structure found in the semiconductors, which is the same as for insulators except that the band gap is relatively narrow (<2 eV)

Answer 15

empty conduction band, band gap, filled valence band

Question 16

for metals nearby energy states are accessible by thermal fluctuations

Answer 16

energy states

Question 17

higher energy states not accessible due to gap (>2 eV)

Answer 17

insulators

Question 18

higher energy states separated by smaller gap

Answer 18

semiconductors

Question 19

Because crystalline defects serve as scattering centers for conduction electrons in metals, increasing their number raises the resistivity (or lowers the conductivity). The concentration of these imperfections depends on ___ of a metal specimen.

Answer 19

temperature, composition, and the degree of cold work

Question 20

it has been observed experimentally that the total resistivity of a metal is the
sum of the contributions from___; that is, the scattering mechanisms act independently of one another.

Answer 20

thermal vibrations, impurities, and plastic deformation

Question 21

dependence of the thermal resistivity component on temperature is due to the increase with temperature in thermal vibrations and other lattice irregularities (e.g., vacancies), which serve as

Answer 21

electron-scattering centers

Question 22

a single impurity that forms a solid solution, the impurity resistivity pi is related to the___, in terms of the atom fraction (at 100%)

Answer 22

impurity concentration ci

Question 23

also raises the electrical
resistivity as a result of increased numbers of electron-scattering dislocations. The effect of deformation on resistivity

Answer 23

Plastic deformation

Question 24

negative charge

Answer 24

electron

Question 25

equal & opposite positive charge

Answer 25

hole

Question 26

move at different speeds

Answer 26

drift velocity

Question 27

higher temperatures promotes more ___ in the conduction band

Answer 27

electrons

Question 28

pure material semiconductors; e.g., silicon & germanium

Answer 28

group IVA materials

Question 29

compound semiconductors

Answer 29

III - V compounds
II - VI compounds

Question 30

the wider the electronegativity difference between the elements the wider the energy gap

Answer 30

compound semiconductors

Question 31

-no applied electric field
-Si atom

Question 32

because there are two types of charge carrier (free electrons and holes) in an ____, the expression for electrical conduction, must be modified to include a term to account for the contribution of the hole current

Answer 32

intrinsic semiconductor

Question 33

two types of charge carrier

Answer 33

free electrons and holes

Question 34

for intrinsic semiconductors, every electron promoted across the band gap leaves behind a hole in the ___

Answer 34

valence band

Question 35

no. of electrons = no. of holes (n=p)

case for pure Si

Answer 35

intrinsic conduction

Question 36

no. of electrons not equal to no. of holes

occurs when impurities are added with different no. of valence electrons than the host

Answer 36

extrinsic conduction

Question 37

two extrinsic types

Answer 37

n-type and p-type

Question 38

( n&raquo_space; p )

Answer 38

n-type extrinsic

Question 39

( p&raquo_space; n )

Answer 39

p-type extrinsic

Question 40

example of n-type extrinsic

Answer 40

phosphorus atom

Question 41

example of p-type extrinsic

Answer 41

boron atom