Catégorie

Transition de phase

vignette|droite|Noms exclusifs des transitions de phase en thermodynamique. En physique, une transition de phase est la transformation physique d'un système d'une phase vers une autre, induite par la variation d'un paramètre de contrôle externe (température, champ magnétique...). Une telle transition se produit lorsque ce paramètre externe atteint une valeur seuil (ou valeur « critique »). La transformation traduit généralement un changement des propriétés de symétrie du système. Quelques exemples : les changements d'état de la matière : fusion, ébullition, sublimation ; les changements de propriétés magnétiques : un métal ferromagnétique passe d'un comportement ferromagnétique à paramagnétique au-delà du point de Curie ; certains matériaux deviennent supraconducteurs en dessous d'une température critique ; la condensation quantique de fluides bosoniques en condensat de Bose-Einstein ; les brisures de symétrie dans les lois de la physique au début de l'histoire de l'Univers, en lien avec son expansion et la diminution de sa température ; la transition de phase que semble subir la matière nucléaire à certaines énergies. Les transitions de phase ont lieu lorsque l'enthalpie libre G (aussi appelée énergie libre de Gibbs) d'un système n'est pas une fonction analytique (par exemple non continue ou non dérivable) pour certaines variables thermodynamiques. Cette non-analyticité provient du fait qu'un nombre extrêmement grand de particules interagissent ; cela n'apparaît pas lorsque les systèmes sont trop petits. Changement d'état vignette|redresse=1.5|Représentation schématique des changements d'états les plus courants. Les transitions de phase (ou changements d'état physique) les plus courantes font intervenir trois états de la matière, l'état solide, l'état liquide et l'état gazeux, elles sont donc au nombre de six : de solide à liquide : fusion ; de solide à gazeux : sublimation ; de liquide à solide : solidification ; de liquide à gazeux : vaporisation (ébullition ou évaporation) ; de gazeux à solide : condensation solide, déposition ou sublimation inverse ; de gazeux à liquide : liquéfaction ou condensation liquide ; En thermodynamique, un terme spécifique est attribué à chacune des transitions.

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Exercices associés (32)

Cylindre ferromagnétique

An infinite cylinder of ferromagnetic material carries a uniform magnetization

{\bf M}

. What is the current density linked to the surface of the cylinder? Determine the fields

{\bf B}

and

{\bf H}

inside and outside of the cylinder. At the surface of the magnetized cylinder a linked current whose density(current per unit length) is

{\bf K}_b=M\,{\bf \hat{\phi}}

is circulating. The surface of the cylinder is behaving like an infinite coil that carries the same current density. So

{\bf B}={\bf H}=0

Gauss s law for magnetism

A Gaussian surface in the shape of a right circular cylinder has a radius of 13u2006cm and a length of 80u2006cm. Through one end there is an inward magnetic flux of 25u2006μWb, where

1\,{\rm Wb\,(Weber)} = 1\,{\rm T}\cdot {\rm m}^2

. At the other end there is a uniform magnetic field of 1.6u2006mT, normal to the surface and directed outward. Calculate the net magnetic flux through the curved surface. Total flux of magnetic field through a closed surface is equal to 0 according to the Gauss’s law for magne

Sphère sur un plan incliné

A non-conducting sphere of mass Mu2004=u200480g and of radius Ru2004=u200420cm is surrounded by a coil with 5 turns. The sphere is initially placed on an inclined plane (angle θ), such that the coiling are parallel to the inclined plane. The system is subject to a uniform vertical magnetic field Bu2004=u20040.35T. Which current in the coil would allow to kkep the sphere in balance on the inclined plane ? Show that the result does not depend on θ. [N.B. : The sphere cannot slip.] The sphere is in balance.

Le siphon

We use the siphon of the figure to empty a container of water. At the exit of the tube, the shrinking factor is 0.6. i) What is the water velocity at the exit of the tube? ii) What is the maximal height of the siphon if we want to avoid the formation of bubbles (cavitation) at the top of the siphon? The vapor pressure of water is P_(sat)u2004=u20041765 Pa. The edge of the siphon is located 2m under the bottom of the container. The flow is sufficiently weak so that we can consider the height of fluid constan

Exercices associés (32)

Cylindre ferromagnétique

An infinite cylinder of ferromagnetic material carries a uniform magnetization

{\bf M}

. What is the current density linked to the surface of the cylinder? Determine the fields

{\bf B}

and

{\bf H}

inside and outside of the cylinder. At the surface of the magnetized cylinder a linked current whose density(current per unit length) is

{\bf K}_b=M\,{\bf \hat{\phi}}

is circulating. The surface of the cylinder is behaving like an infinite coil that carries the same current density. So

{\bf B}={\bf H}=0

Gauss s law for magnetism

A Gaussian surface in the shape of a right circular cylinder has a radius of 13u2006cm and a length of 80u2006cm. Through one end there is an inward magnetic flux of 25u2006μWb, where

1\,{\rm Wb\,(Weber)} = 1\,{\rm T}\cdot {\rm m}^2

Sphère sur un plan incliné

Le siphon

Notebooks associés (16)

Classical Monte Carlo Simulations of the Ising Model on Square Lattice

"## Classical Monte-Carlo simulations of the Ising model on square lattice\n", "\n", "The Ising model considers the following Hamiltonian\n", "\n", "

\\hat{\\mathcal{H}} = -J\\displaystyle\\sum_{}\\sigma_i \\sigma_j

,\n", "\n", "in which spins

\\sigma_i

can take only two discrete values

\\sigma_i \\in \\{-1,+1\\}

. Below, we will consider spins on two-dimensional square lattice taking into account couplings

J

only for the nearest neighbor sites. For

J > 0

the ferromagneti

Density of States in Magnetic Fields Using Landau Levels

Start by setting some parameters including an (artificial) analytical expression of the Fermi surface along kz direction"

"### Define some expressions according to Landau quantization, such as the energy spacing and projection area in k-space"

Set up a histogram to count interceptions between the Fermi surface and "Landau tubes", compute density of states"

Exploring Chemical Potential for Fermions in 3D at Finite Temperature

This notebook gives a simple illustration to the variation of chemical potential for Fermions in 3D, following the Fermi-Dirac statistics in finite temperature. " In 3D, we have the density of states

\\rho \\propto \\sqrt{E}

. At zero temperature, the distribution of electrons just follows

g(E)=a \\sqrt{E}

and the Fermi energy is determined by the total occupied number

N_{occ}

E_f

is the energy such that

N_{occ}=\\int_{0}^{E_f} g(E) dE

\n", " \n", "In finite temperature, however, o

Investigating the Effect of Phase on Sound Perception

Hearing the phase of a sound[1]¶

                                      [2]Paolo Prandoni, [3]LCAV, EPFL

In this notebook we will investigate the effect of phase on the perceptual quality of a sound. It is often said that the human ear is commercial-grade audio equipment takes place in the magnitude domain only. In [1]: %matplotlib inline import matplotlib import matplotlib.pyplot as plt import numpy as np import IPython from scipy.io import wavfile In [2]: plt.rcParams["figure.fig

Transition de phase

Chattez avec Graph Search

Sequential hybrid self-assembled monolayers enabling uniform coverage and efficient hole extraction in perovskite photoelectronics

Proximity Induced Magnetic Anisotropy and Trefoil Fermiology in Monolayer FeCl 2 /Bi(111)

Nonreciprocity and High-Frequency Dynamics in Curved and Chiral Superconducting and Ferromagnetic Nanostructures

Start by setting some parameters including an (artificial) analytical expression of the Fermi surface along kz direction"

Set up a histogram to count interceptions between the Fermi surface and "Landau tubes", compute density of states"

Start by setting some parameters including an (artificial) analytical expression of the Fermi surface along kz direction"

Set up a histogram to count interceptions between the Fermi surface and "Landau tubes", compute density of states"

Sequential hybrid self-assembled monolayers enabling uniform coverage and efficient hole extraction in perovskite photoelectronics

Proximity Induced Magnetic Anisotropy and Trefoil Fermiology in Monolayer FeCl 2 /Bi(111)

Nonreciprocity and High-Frequency Dynamics in Curved and Chiral Superconducting and Ferromagnetic Nanostructures