What is meant by a free electron?
1 : an electron within a conducting substance (as a metal) but not permanently attached to any atom. 2 : an electron moving in a vacuum.
Who proposed free electron model?
Hendrik A.
What are the types of free electron theory?
Classical free electron theory of metals (Drude – Lorentz theory of metals): Drude and Lorentz proposed this theory in 1900. According to this theory, the metals containing the free electrons obey the laws of classical mechanics. directions. kinetic theory of gases.
What are the limitations of free electron theory?
(c) It cannot explain why the observed specific heat of metals is only 1% of the calculated value (i.e., 3/2 N KB; N are number of free electrons per gram atom). (d) It cannot explain the temperature variation of the electrical conductivity. (e) It cannot explain the paramagnetic behaviour of metals.
What is Lorentz theory?
Lorentz-Drude proposed that conductors like metals contain a large number of free electrons. The positive ions are fixed in their locations. ( The arrangement of the positive ions is called lattice). The negative ions (electrons) move randomly in lattice in an open circuit.
What is Drude theory of conductor?
The Drude model of electrical conduction was proposed in 1900 by Paul Drude to explain the transport properties of electrons in materials (especially metals). Later it was supplemented with the results of quantum theory in 1933 by Arnold Sommerfeld and Hans Bethe, leading to the Drude–Sommerfeld model.
What is Drude theory of conduction?
The Drude model considers the metal to be formed of a mass of positively-charged ions from which a number of “free electrons” were detached. The Drude model is a purely classical model, and treats both electrons and ions as solid spheres.
What is the unit of Lorentz number?
The ratio of thermal to electrical conductivity, commonly known as the Lorenz number, is the same for almost all metals at a given temperature T and takes a value around 3(kB/e)2T, where kB and e are the Boltzmann constant and electronic charge, respectively.
What is electronic thermal conductivity?
By definition, electrical conductivity is a measure of how well electrical current (charge in motion) can pass through a material under the influence of an applied voltage/electric field. Thermal conductivity measures how well heat (thermal energy in motion) can pass through a material under a temperature differential.
Is thermal conductivity proportional to electrical conductivity?
thermal conductivity is proportional to electrical conductivity in all materials. thermal conductivity is inversely proportional to electrical conductivity in metals. At low temperatures, conductivity increases with the addition of high valency atoms to the bulk lattice, as they provide more electrons to the lattice.
Is thermal conductivity a physical property?
Conductivity is a physical property because the identity of the substance does not change.
Does thermal conductivity depend on temperature gradient?
Thermal Conductivity Variation The thermal conductivity of a specific material is highly dependent on a number of factors. These include the temperature gradient, the properties of the material, and the path length that the heat follows.
On what factors thermal conductivity depends?
Thermal conductivity depends strongly on moisture, temperature and structure of the material.
What is a good conductivity level in water?
Distilled water has a conductivity in the range of 0.5 to 3 µmhos/cm. The conductivity of rivers in the United States generally ranges from 50 to 1500 µmhos/cm. Studies of inland fresh waters indicate that streams supporting good mixed fisheries have a range between 150 and 500 µhos/cm.