Chapter 7: Electrical Properties Flashcards
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
Ohm’s law
Ohm’s law
V = IR
The ___ ρ is
independent of specimen geometry but related to R
electrical resistivity
The value of R is influenced by ___, and for many
materials is independent of current.
specimen configuration
is used to specify the
electrical character of a material. It is simply the reciprocal of
the resistivity
electrical conductivity σ
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.
electric current
Within most solid materials a current arises from the flow of
electrons, which is termed
electronic conduction
for ionic materials a net motion of charged ions is possible that
produces a current; such is termed
ionic conduction
filled - highest occupied energy levels
valence band
empty - lowest unoccupied energy levels
conduction band
Four possible electron band structures for
solid materials
The various possible electron band structures in solid at 0 K
-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
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
empty band, band gap, empty states, filled states
The electron band structure of metals such as magnesium, wherein there is an overlap of filled and empty outer bands
empty band, filled band
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)
empty conduction band, band gap, filled valence band
- (conductors)
- thermal energy puts many electrons into a higher energy state
metals
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)
empty conduction band, band gap, filled valence band
for metals nearby energy states are accessible by thermal fluctuations
energy states
higher energy states not accessible due to gap (>2 eV)
insulators
higher energy states separated by smaller gap
semiconductors
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.
temperature, composition, and the degree of cold work
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.
thermal vibrations, impurities, and plastic deformation
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
electron-scattering centers
a single impurity that forms a solid solution, the impurity resistivity pi is related to the___, in terms of the atom fraction (at 100%)
impurity concentration ci
also raises the electrical
resistivity as a result of increased numbers of electron-scattering dislocations. The effect of deformation on resistivity
Plastic deformation
