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Related Concept Videos

Carrier Transport01:21

Carrier Transport

The generation of electrical current in semiconductors is fundamentally driven by two mechanisms: drift and diffusion. These processes are essential for the functionality and performance of semiconductor-based devices.
Drift Current:
The drift of charge carriers is started by an external electric field (E). Charged particles, such as electrons and holes, experience an acceleration between collisions with lattice atoms. For electrons, this results in a drift velocity (vd) given by:
Atomic Nuclei: Nuclear Spin State Population Distribution01:14

Atomic Nuclei: Nuclear Spin State Population Distribution

Near absolute zero temperatures, in the presence of a magnetic field, the majority of nuclei prefer the lower energy spin-up state to the higher energy spin-down state. As temperatures increase, the energy from thermal collisions distributes the spins more equally between the two states. The Boltzmann distribution equation gives the ratio of the number of spins predicted in the spin −½ (N−) and spin +½ (N+) states.
Free Energy and Equilibrium02:56

Free Energy and Equilibrium

The free energy change for a process may be viewed as a measure of its driving force. A negative value for ΔG represents a driving force for the process in the forward direction, while a positive value represents a driving force for the process in the reverse direction. When ΔGrxn is zero, the forward and reverse driving forces are equal, and the process occurs in both directions at the same rate (the system is at equilibrium).
Recall that Q is the numerical value of the mass action expression...
Free Energy and Equilibrium00:55

Free Energy and Equilibrium

The free energy change for a process may be viewed as a measure of its driving force. A negative value for ΔG represents a driving force for the process in the forward direction, while a positive value represents a driving force for the process in the reverse direction. When ΔG is zero, the forward and reverse driving forces are equal, and the process occurs in both directions at the same rate (the system is at equilibrium).
The reaction quotient, Q, is a convenient measure of the status of an...
Joule-Thomson Effect01:21

Joule-Thomson Effect

The Joule-Thomson effect, also known as the Joule-Kelvin effect, describes the temperature change of a fluid when it is forced through a valve or porous plug while keeping it in a thermally insulated environment. This experiment is called a throttling process. This is an important effect widely used in refrigeration and the liquefaction of gases.
This experiment forces high-pressure gas through a throttle valve or a porous plug to a lower-pressure region. The gas expands as it passes through to...
Phase Transitions: Melting and Freezing02:39

Phase Transitions: Melting and Freezing

Heating a crystalline solid increases the average energy of its atoms, molecules, or ions, and the solid gets hotter. At some point, the added energy becomes large enough to partially overcome the forces holding the molecules or ions of the solid in their fixed positions, and the solid begins the process of transitioning to the liquid state or melting. At this point, the temperature of the solid stops rising, despite the continual input of heat, and it remains constant until all of the solid is...

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Related Experiment Video

Updated: May 26, 2026

Non-equilibrium Microwave Plasma for Efficient High Temperature Chemistry
07:17

Non-equilibrium Microwave Plasma for Efficient High Temperature Chemistry

Published on: August 1, 2017

Electron temperature gradient scale at collisionless shocks.

Steven J Schwartz1, Edmund Henley, Jeremy Mitchell

  • 1Blackett Laboratory, Imperial College London, South Kensington, United Kingdom. s.schwartz@imperial.ac.uk

Physical Review Letters
|December 21, 2011
PubMed
Summary
This summary is machine-generated.

This study reveals that electron heating in astrophysical shock waves occurs within narrow layers, a key factor limiting nonlinear steepening and influencing cosmic ray acceleration. Understanding these electron dynamics is crucial for space physics.

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Characterization of Thermal Transport in One-dimensional Solid Materials
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Last Updated: May 26, 2026

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Experimental Methodology for Estimation of Local Heat Fluxes and Burning Rates in Steady Laminar Boundary Layer Diffusion Flames
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Published on: January 26, 2014

Area of Science:

  • Space Physics
  • Astrophysics
  • Plasma Physics

Background:

  • Shock waves are fundamental in space and astrophysics, converting flow energy to heat and accelerating particles.
  • While large-scale ion heating is understood, electron heating and small-scale electromagnetic fields within shock layers remain poorly characterized.

Purpose of the Study:

  • To determine the spatial scale of the electron temperature gradient in shock waves.
  • To investigate the relationship between electron heating, electromagnetic fields, and shock properties.

Main Methods:

  • In situ measurements of electron distributions using the Cluster spacecraft.
  • Analysis of electron temperature gradients and electromagnetic field structures within shock layers.

Main Results:

  • Electron heating occurs within a narrow layer, approximately several electron inertial lengths (c/ωpe) thick.
  • This narrow heating layer limits nonlinear steepening due to wave dispersion.
  • The DC electric field also varies on these small scales.

Conclusions:

  • The scale of electron heating is determined, providing insights into energy dissipation in shock waves.
  • Wave dispersion limits nonlinear steepening in these astrophysical shocks.
  • Small-scale electric field variations significantly impact the efficiency of cosmic ray acceleration by shocks.