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Flashcards in Electrical Conductivity in Metals Deck (90)
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1

According to Classical Free Electron Theory, what are free electrons ?

Freely moving valence electrons, confined to body

2

How does an applied electric field cause current in a metal, according to CFET ?

Current is a consequence of drift velocity of free electrons

3

What is the direction of the drift velocity of the free electrons(Conduction electrons) ?

Opposite to the applied electric field

4

What are free electrons equivalent to in CFET ?

Gas molecules

5

What are the expected to obey

Laws of Kinetic Theory of Gases

6

What is the energy associated with each electron in the absence of an electric field ?

(3/2)KT

7

What is K ?

Boltzmann Constant

8

What is the electric potential due to ionic cores ?

It is essentially constant throughout the metal

9

What is the magnitude of the force of attraction between the free electrons and the lattice ions ?

It is negligible

10

What about the repulsive force in between electrons ?

It is also negligible

11

What is mean free path, according to Kinetic Theory of Gases ?

It it the AVERAGE distance in between two successive collisions

12

Collisions of what ?

Collisions of two other molecules

13

How is it defined in CFET ?

It is the average distance travelled by the conduction electrons in between two successive collisions

14

Collisions with what ?

Lattice ions

15

What is mean collision time ?

It is the average TIME elapsed between two successive collisions

16

Collisions of what ?

An electron with lattice points

17

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

18

What is current density ?

It is the current per unit area

19

Area of what ?

Cross section of an imaginary plane

20

What is the orientation of this imaginary plane ?

It is held normal to the direction of current

21

What is electric field ?

It is the potential drop per unit length of a conductor

22

What kind of conductors is this applicable to ?

Homogeneous conductors (Otherwise, integration is required)

23

What physical property does conductivity characterize ?

The conducting ability of a material

24

How is it quantified ?

It is the inverse of resistivity

25

What is mobility of an electron ?

It is the drift velocity acquired by electrons in unit field

26

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

27

How did CFET predict temperature dependence of electrical conductivity ?

Directly proportional to square root of temperature ?

28

How was it found to be experimentally ?

Inversely proportional to temperature

29

How did CFET say electrical conductivity depends on electron concentration ?

Electrical conductivity is directly proportional to electron concentration

30

What was the practical contradiction ?

The conductivites of Copper and Silver are much higher than Zinc and Cadmium