Flashcards in Electrical Conductivity in Metals Deck (90)
According to Classical Free Electron Theory, what are free electrons ?
Freely moving valence electrons, confined to body
How does an applied electric field cause current in a metal, according to CFET ?
Current is a consequence of drift velocity of free electrons
What is the direction of the drift velocity of the free electrons(Conduction electrons) ?
Opposite to the applied electric field
What are free electrons equivalent to in CFET ?
What are the expected to obey
Laws of Kinetic Theory of Gases
What is the energy associated with each electron in the absence of an electric field ?
What is K ?
What is the electric potential due to ionic cores ?
It is essentially constant throughout the metal
What is the magnitude of the force of attraction between the free electrons and the lattice ions ?
It is negligible
What about the repulsive force in between electrons ?
It is also negligible
What is mean free path, according to Kinetic Theory of Gases ?
It it the AVERAGE distance in between two successive collisions
Collisions of what ?
Collisions of two other molecules
How is it defined in CFET ?
It is the average distance travelled by the conduction electrons in between two successive collisions
Collisions with what ?
What is mean collision time ?
It is the average TIME elapsed between two successive collisions
Collisions of what ?
An electron with lattice points
What is the probability of finding an electron moving in any given direction equal to ?
The probability of finding another electron in exactly the opposite direction in the ABSENCE of a field
What is current density ?
It is the current per unit area
Area of what ?
Cross section of an imaginary plane
What is the orientation of this imaginary plane ?
It is held normal to the direction of current
What is electric field ?
It is the potential drop per unit length of a conductor
What kind of conductors is this applicable to ?
Homogeneous conductors (Otherwise, integration is required)
What physical property does conductivity characterize ?
The conducting ability of a material
How is it quantified ?
It is the inverse of resistivity
What is mobility of an electron ?
It is the drift velocity acquired by electrons in unit field
What was the contradiction of CFET in terms of molar specific heat of a gas at constant volume ?
It was found to be temperature dependent
How did CFET predict temperature dependence of electrical conductivity ?
Directly proportional to square root of temperature ?
How was it found to be experimentally ?
Inversely proportional to temperature
How did CFET say electrical conductivity depends on electron concentration ?
Electrical conductivity is directly proportional to electron concentration