A charge carrier transports electric charge by moving: electrons are one example, and ions are another. For species with number density , electric charge and mean velocity , the transport contributions add as . A stationary charged background contributes to charge density but not to this current density. [ref].
The drift velocity is a charge carrier population's mean velocity relative to its material's rest frame. It describes the net transport superposed on microscopic motion. For a single species, current density is ; for electrons, reverses the direction. It is distinct from the propagation speed of an electrical disturbance. [ref].
The mean velocity of the electron population associated with a net electric current, distinct from random thermal or Fermi motion. Its sign is opposite to conventional current for negative charge carriers. Its usually small magnitude is not the propagation speed of an electromagnetic signal in a transmission line.
For sinusoidal current density and constant carrier density , the electron drift velocity is . Its displacement has amplitude and zero net change over a full cycle. The distance accumulated by this drift alone in one cycle is . With an RMS current, . This does not measure the much larger microscopic path due to Fermi velocity and electron-phonon scattering.
A charge carrier population per unit volume or, for a sheet, per unit area. The dimensional convention and whether different carrier species are counted separately must be specified.
Charge carrier mobility is the magnitude of steady drift velocity per unit weak electric field in a scalar transport model. In the Drude model, and . The positive charge carrier mobility separates ease of motion from the sign of electric charge; its SI unit is .
A transport quantity obtained by combining longitudinal electrical conductivity and a Hall coefficient. It equals single-carrier drift mobility only under the corresponding one-carrier and scattering assumptions. This does not independently determine effective mass and scattering time.
The positive hole mobility is the magnitude of an electron hole's weak-field drift velocity per unit electric field. In an isotropic relaxation-time model, , and its contribution to electrical conductivity is . The sign is opposite to an electron's drift because the electron hole has positive charge.
The positive electron mobility relates the drift velocity of conduction electrons to an electric field: . In the isotropic Drude model, , where is the momentum relaxation time and the band effective mass. The minus sign describes negative charge; the electron mobility itself is positive.

Ancestors (7)

  1. Current density
  2. Electric current
  3. Electric charge
  4. Electromagnetism
  5. Branches of physics
  6. Physics
  7. Home

Incoming links (50)

View article source

Discussion (0) New discussion

There are no discussions about this article yet.

Articles by others on the same topic (1)

Charge carrier by Wikipedia Bot 1
View more
A charge carrier is a particle or entity that carries an electric charge and is responsible for electrical conduction in a material. In the context of solid materials, charge carriers can be classified primarily into two types: 1. **Electrons**: Negative charge carriers that are typically found in conductive materials like metals and semiconductors. They move through the material to conduct electricity. 2. **Holes**: Positive charge carriers that can be considered as the absence of an electron in a semiconductor.
Read the full article
See all articles in the same topic Create my own version