What is Drude theory of conduction?
The Drude model of electrical conduction was proposed in 1900 by Paul Drude to explain the transport properties of electrons in materials (especially metals). Basically, Ohm’s law was well established and stated that the current J and voltage V driving the current are related to the resistance R of the material.
What is Drude model explain the postulates of Drude model?
The Drude model is the application of kinetic theory to electrons in a solid. It assumes that the material contains immobile positive ions and an “electron gas” of classical, non-interacting electrons of density ‘n’.
What is classical theory of conductivity in metals?
Assumptions of Classical free-electron theory: All metals contain large number of free electrons which move freely through the positive ionic core of the metals. Since these free electrons causes conduction in metal under the application of electrical field, they are called as conduction electrons.
What is free electron theory of metals?
The treatment of a metal as containing a gas of electrons completely free to move within it. The theory was originally proposed in 1900 to describe and correlate the electrical and thermal properties of metals.
What are the assumption of Drude model?
Drude model assumes that the mean electronic velocity at a point vanishes – this cannot be rigorously justified. Electrons coming from the higher temperature side will have higher energy and hence a higher speed – net motion of electrons from higher temperature side to lower temperature side.
What was the key modification to Drude theory made by Sommerfeld?
Sommerfeld Drude model: – Retains almost all aspects of Drude model with the following modifications: 1. Treats electrons using FD statistics. 2. Recognizes that their energies are discrete – treats them like a particle in a box of constant energy.
Why the Drude model is known as the classical free electron theory?
The classical free electron theory was proposed by Drude and Lorentz in 1900. This theory said that metals with free electrons obey the laws of classical mechanics. 1. The valence electrons contained in an atom, are free to move about the whole volume of the metal, as the molecules of a perfect gas move in a container.
What does the conductivity of metals depend upon?
The heat conductivity of a metal is dependent on two main factors: 1) number of free electrons, 2) speed of the free electrons and especially how far they can travel before they bump into some atoms and change their direction.
What is classical conduction?
In the classical model, it is assumed that a free electron is accelerated for a short time and then collides with a lattice ion. After the collision, the velocity of the electron is assumed to be completely unrelated to that before the collision.
What is the significance of free electron theory?
The free electron model solved many of the inconsistencies related to the Drude model and gave insight into several other properties of metals. The free electron model considers that metals are composed of a quantum electron gas where ions play almost no role.
Which one of following is not explained by Drude model?
The Drude model cannot explain the conductivity of alloys. Even small impurities can drastically decrease the conductivity of metals in a way which is not predicted by the Drude model. From a classical mechanics perspective, the electrons should contribute greatly to the heat capacity of metals.
What is Sommerfeld theory of free electrons?
The Sommerfeld free electron model treats electrons as free particles with energy dispersion ε = ℏ 2 k 2 2 m . The density of states follows from the dispersion relation by using a general procedure that is analogous to that for phonons.
What are the Limitaions of electron theory given by Sommerfield?
(ii) It could not explain the distribution and arrangement of electrons in atoms. (iii) Sommerfeld’s model was unable to explain the spectra of alkali metals such as sodium, potassium etc. (iv) It could not explain Zeeman and Stark effect.
Which phenomenon Drude free electron theory Cannot explain?
1) It fails to explain the electrical conductivity of semiconductors and insulators. temperature. 3) It fails to explain the concept of specific heat of metals.
Are free electrons in the valence band or in the conduction band?
electrical conduction …by electrons is the valence band. In a conductor, the valence band is partially filled, and since there are numerous empty levels, the electrons are free to move under the influence of an electric field; thus, in a metal the valence band is also the conduction band.
What is the role of 4 valence electrons on electrical conductivity?
The elements or materials can not conduct electric current as efficiently as a conductor and at the same time, they cannot block the flow of current through them. The conductivity of these elements which have four valence electrons is moderate that is not good as well as not bad.
What are the important properties of metal explained by classical free electron theory?
Classical free electron theory: The first theory was developed by Drude and Lorentz in 1900. According to this theory, metal contains free electrons which are responsible for the electrical conductivity and electrons obey the laws of classical mechanics.
Who proposed classical free electron theory?
1. Classical free electron theory: The first theory was developed by Drude and Lorentz in 1900.
What are the main assumption of quantum free electron theory?
Assumptions of Quantum Free Electron Theory 1) Valence electrons move freely in a constant potential within the boundaries of metal and is prevented from escaping the metal at the boundaries (high potential). Hence the electron is trapped in a potential well.