Postulates of classical free electron theory 1 the free electrons of a metal are having like the moleculesof a gas in acontainer. Jun 15, 2018 these free electrons move freely throughout the lattice and hence are termed as electron gas. Dec 03, 2012 unit1 classical free electron theory physics. It was developed in 1927, principally by arnold sommerfeld, who combined the classical drude model. What is the main difference between classical free. In solidstate physics, the free electron model is a simple model for the behaviour of charge carriers in a metallic solid. A classical theory of the electron, proposed by one of us several years ago and based on finitedifference equations, is discussed by considering the three possible following cases. What is the main difference between classical free electron theory and quantum free electron theory. Arnold sommerfeld considered quantum theory and extended the theory to the free electron model, where the carriers follow fermidirac distribution.
That time the valance electrons in metals were regarded as the noninteracting particles of an ideal gas. Describe the classical free electron model of metals in terms of the concept electron number density. It is possible that many electron may possess same energy. According to classical free electron theory of metals electrical conductivity is given by, from the above equation, relation between temperature and electrical conductivity is given by hence, classical free electron fails to explain the temperature dependence of electrical conductivity. Quantum free electron theory could successfully explain the electronic sp. The electron has a mass that is approximately 11836 that of the proton. These limitations of the classical theory were overcome to a large extent by sommerfeld who argued that free electrons in a metal behave as quantum mechanical. Atomic selectrons are delocalised due to overlap of outer orbits. Classical free electron theory this theory was developed by drude and lorentz. Jan 31, 2011 drawbacks of classical free electron theory 1. Unit1 classical free electron theory physics youtube. Apr 29, 2020 classical free electron theory of metals engineering physics edurev notes is made by best teachers of civil engineering ce.
Unit iii free electron theory engineering physics dr. Although the free electron model is a great oversimplification of the reality, surprisingly in many cases it works pretty well, so that it is able to describe many important properties of metals. The phenomena such a photoelectric effect, compton effect and the black body radiation couldnt be explained by classical free electron theory. Freeelectron theory of metals article about freeelectron. His approach is based upon quantization of electrical energy levels. The free electron theory of metals using classical laws was developed by dude and lorentz in the beginning of last century. Apr 10, 20 the phenomena such a photoelectric effect, compton effect and the black body radiation couldnt be explained by classical free electron theory. Classical theory states that all free electrons absorb the supplied energy. He realised the role played by pauli exclusion principle in restricting the. Classical theory of freeelectron lasers a text for students and researchers eric b szarmes chapter 1 introduction and overview 1.
Classical free electron theory, physics experts mind. Engineering physics ii unit 1 conducting materials notes. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no known components or substructure. A physics 12 talk titled the classical free electron theory. Metalsdrudes classical theory theory by paul drude in 1900, only three years after the electron was discovered. B m s institute of technology classical free electron theory. The simplest metals are the alkali metals lithium, sodium, potassium, na, cesium, and rubidium. Electron gas history electron gas model predates quantum mechanics electrons discovered in 1897 drudelorentz model 1905electrons classical particles free to move in a box model. According to classical theory, which follows maxwell.
The electrons move in a constant potential inside the. Free electron model of metals, in solidstate physics, representation of a metallic solid as a container filled with a gas composed of free electrons i. But quantum theory states that only a few electron absorb the supplied energy. What is the main difference between classical free electron. Classical, nonrelativistic theory of scattering of electromagnetic radiation we present here the theory of scattering of electromagnetic radiation from the classical, nonrelativistic physics approach. Page 3 mobility of electrons the mobility of electrons is defined as the magnitude of drift velocity acquired by the electron in a unit field. The theory has been developed in three main stages. The theory was originally proposed in 1900 to describe and correlate the electrical and thermal properties of metals. Give the assumptions of the classical free electron theory. Sommerfelds free electron theory of metals physics assignment. Engineering physics ii unit 1 conducting materials. Most of the free electron radiation schemes of emission or acceleration operate in the classical theoretical regime of electrodynamics, where the electrons can be considered pointparticles and the radiation field is described by maxwell equations no field.
Quantum free electron theory was proposed by arnold sommerfeld. Jan 20, 2020 describe the classical free electron model of metals in terms of the concept electron number density. Calculate the energy levels and energylevel spacing of a free electron in a metal. A metal is imagined as the structure of 3dimensional array of ions in between which, there are free moving valence electrons confined to the body of the material. Classical free electron theory of metals engineering. In 1998 he joined the faculty of the university of hawaii where he is currently an associate professor of physics. Classical theory of free electron lasers a text for students and researchers eric b szarmes chapter 1 introduction and overview 1. Amazingly, the conductivity predicted turns out to be the same as in the drude model, as it does not depend on the form of the electronic speed distribution. Drudes theory treated the electrons as an ordinary classical gas. Assumptions or salient features in classical free electron theory the classical free electron theory is based on the following postulates. Neglecting the electron electron interaction and the electron ion interaction, it appears as if the electrons move in a confined box with periodic collision with ions in the lattice. Explain the quantum freeelectron model of metals in terms of paulis exclusion principle. The free electrons, considered identical to the outermost, or valence.
Free classical electrons l consider a gas of free classical electrons moving under the influence of electric and area a magnetic fields. Apr 19, 2019 free electron theory of conductor was proposed by p. Nov 05, 2016 quantum free electron theory could successfully explain the electronic sp. Calculate the energy levels and energylevel spacing of a. Hence, classical free electron fails to explain the temperature dependence of electrical conductivity. Write down the drawbacks of classical free electron theory. This textbook focuses on the fully classical theory of fels with application to fel oscillators and develops the fundamentals of fel theory in sufficient depth to provide both a solid understanding of fel physics and a solid background for research in the field. Chapter 6 free electron fermi gas national tsing hua. Theory advanced of theory light emission and application to free electron lasers advanced texts in physics. So it leads to much larger predicted quantities than that is actually observed. Read online classical theory of iopscience book pdf free download link book now. Classical, nonrelativistic theory of scattering of. The dude model is the application of kinetic theory to electrons in a solid.
In 1928, by applying quantum mechanical principles, arnold sommerfeld succeeded in overcoming many of drawbacks of the classical free electron theory, while retaining all the essential features of the classical free electron theory. Sommerfield model for free electron theory 11 success of quantum free electron theory according to classical theory, which follows maxwellboltzmann statistics, all the free electrons gain energy. All books are in clear copy here, and all files are secure so dont worry about it. The valence electrons of the constituent atoms become conduction electrons and move about freely through the volume of the metal. Jan 26, 2009 what is the main difference between classical free electron theory and quantum free electron theory. Classical free electron theory permits all electrons to gain energy. This theory is called quantum free electron theory. Drude in 1900 and developed by lorentz in 1909 to explain electrical conduction in selection from engineering physics book. According to this theory, a metal consists of electrons which are from to move about in the crystal molecules of a gas it contains mutual repulsion between electrons is ignored and hence potential energy is taken as zero therefore the. According to classical theory, the free electrons in a metal have random motions with equal probability in all directions. Classical free electron theory could not explain many physical properties. These free electrons move freely throughout the lattice and hence are termed as electron gas. So, there collective behavior is not describe by classical maxwell.
What are the drawbacks of classical free electron theory. Classical theory of iopscience pdf book manual free. Srit unit iii free electron theory engineering physics. The valence electrons of atoms are free to move about the whole volume of the metal, like the molecules of a perfect gas in a container. Ravindran, sommerfield model for free electron theory uio. Ravindran, phy075 condensed matter physics, spring 20 16 july. According to the classical free electron theory the value of specific heat of metals is given by 4. The free electrons, which constitute the electron gas can have continuous energy values. Put free electrons into a very wide potential well the same size as. The energy values of the free electrons are discontinuous because of which the energy levels are discrete. Classical theory of freeelectron lasers book iopscience.
Free electron theory of conductor was proposed by p. Ohmsohms lawlaw andand electronelectron driftdrift electric fieldelectric field e drift velocity v d current densitycurrent densityjij ia volume element. As per his investigation, the behavior of free electron in different possible energy states is explained, how the large number of electrons are disturbed in the energy states. Pdf free electron theory 201516 vtu shashank mohan. This document is highly rated by civil engineering ce students and has been viewed 10677 times. The treatment of a metal as containing a gas of electrons completely free to move within it. Freeelectron model of metals, in solidstate physics, representation of a metallic solid as a container filled with a gas composed of free electrons i. According to classical free electron theory of metals electrical conductivity is given by, from the above equation, relation between temperature and electrical conductivity is given by. In a metal the available free electrons are fully responsible for electrical conduction. Mar, 2017 start free trial sign in engineering physics by s. Assumptions of classical free electron model 1 there exists a large no of free electron inside the metal they are having 3d freedom. Quantum free electron theory of metals science key. In 1928, sommerfeld developed a new theory applying quantum mechanical concepts and fermidirac statistics to the free electrons in the metal.
The classical theory had several conspicuous successes, notably the. It was developed in 1927, principally by arnold sommerfeld, who combined the classical drude model with quantum mechanical fermidirac statistics and hence it is also known as the drudesommerfeld model. The main assumptions of classical free electron theory are. Free electron theory of metals request pdf researchgate. But same model predicted that all electrons contribute to heat capacity.
Sommerfeld 1928 applied the principles of quantum mechanics to classical free electron theory. Assumptions postulates of quantum free electron theory 1. Boltzmann statistics, all the free electrons gain energy. The classical theory had several conspicuous successes, notably the derivation of the form of ohms law and the. The electrical conductivity of semiconductor and insulator cannot be explained by this theory. His current research interests include the theory and design of novel optical resonators for highresolution free electron laser spectroscopy, xray generation and highfield physics. Drude treated the free electrons as a classical ideal gas but the electrons should collide with the stationary ions, not with each other. A quantummechanical, fullyrelativistic of this subject matter can.
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