Galvanomagnetic effects

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In solid-state physics, galvanomagnetic effects are called thermal and electrical effects that occur in a current-carrying conductor in a magnetic field .

The magnetic field acts on the charge carriers via the Lorentz force , which is directed perpendicular to the direction of movement of the electrons. Among other things, this has an impact on the electrical resistance through extended current paths and on the heat transport associated with an electrical current. Some of the effects serve as the basis for measuring devices (e.g. Hall sensor , field plate ).

to form

The basic forms of the galvanomagnetic effect are:

  • Transverse galvanomagnetic effect (magnetic field perpendicular to the direction of the current): The Lorentz force creates an electrical voltage perpendicular (transversal) to the direction of the current ( Hall effect ). In addition, there is a transverse temperature difference ( Ettingshausen effect ). Both effects are linear in the magnetic field strength. The effect is used, for example, in the Hall sensor .
  • Longitudinal galvanomagnetic effect (magnetic field parallel to the direction of current): Due to the deflection of the current paths, the resistance increases in the longitudinal direction, sometimes also called the Thomson effect or galvanomagnetic Thomson effect - not to be confused with the thermoelectric Thomson effect . This is a magnetoresistive effect . The galvanomagnetic Thomson effect is particularly great with bismuth . There is also a longitudinal temperature difference ( Nernst effect - the term is ambiguous as there is also a thermomagnetic Nernst effect ). For reasons of symmetry, the longitudinal effects do not depend on the direction of the magnetic field and are therefore square in the magnetic field strength.
  • Wiegand effect : Under the influence of a changing external magnetic field, the magnetization reversal of ferromagnets does not take place continuously, but in jumps.

Applications

Related effects

Galvanomagnetic effects are closely related to thermomagnetic effects . While with galvanomagnetic effects an electric current and a magnetic field generate a potential or temperature difference, with thermomagnetic effects a heat flow and a magnetic field generate potential and temperature differences. The generation of the potential difference is called the Ettingshausen-Nernst effect (in the transverse direction also called the Nernst effect ), and that of the temperature difference is called the Righi-Leduc effect (transversal) or Maggi-Righi-Leduc effect (longitudinal)

With thermoelectricity (without a magnetic field) a heat flow creates a potential difference and, conversely, a potential difference creates a heat flow.

literature

  • Werner Roddeck: Springer-Vieweg (Ed.): Introduction to Mechatronics 2012, ISBN 978-3-8348-1622-1 .
  • Ekbert Hering, Rolf Martin, Martin Stohrer: Physik für Ingenieure , Springer, 8th edition 2003, p. 685, 10th edition 2007, p. 845

Web links

Individual evidence

  1. ^ A b c d Albert Haug, Franz Haug: Vieweg (ed.): Applied electrical measurement technology: Basics, sensor technology, measured value processing 1993, ISBN 3-528-14567-6 .
  2. ^ Bergmann, Schaefer: Elektrizitätslehre , De Gruyter 1966, p. 486
  3. ↑ For example in Ekbert Hering, Rolf Martin, Martin Stohrer: Physik für Ingenieure , Springer, p. 685
  4. ↑ Bergmann, Schaefer: Elektromagnetismus , 9th edition, De Gruyter 2006, p. 517. The thermoelectric Thomson effect is called there thermogalvanic effect.
  5. ↑ Hering, Martin, Stohrer: Physik für Ingenieure , Springer 2007, p. 845. The Ettingshausen-Nernst effect of the first kind, the reversal of the Ettingshausen effect, is also called the “Nernst effect”.
  6. ↑ kfztech.de: Active wheel speed sensors . Retrieved August 17, 2016.
  7. ↑ Regine Mallwitz: Analysis of eddy current signals with problem-adapted functions for non-destructive material testing . Retrieved August 17, 2016.