Thermomagnetic effects
With thermomagnetic effects , a heat flow in a conductor or semiconductor that is in a magnetic field creates a potential or temperature difference.
With a transverse magnetic field
If, due to a given temperature difference, a heat flow flows in a direction x and an external magnetic field acts perpendicular to it (direction z ), the following effects are observed:
- Nernst effect (also known as the first Ettingshausen-Nernst effect ): a potential difference (electrical voltage) in direction y , i.e. perpendicular to the heat flow and perpendicular to the magnetic field.
- Righi-Leduc effect (also called thermal Hall effect ): a temperature difference in direction y , i.e. perpendicular to the heat flow and perpendicular to the magnetic field.
The cause lies in the effect of the Lorentz force on the moving charge carriers (mostly electrons).
With a longitudinal magnetic field
If the external magnetic field acts longitudinally (parallel to the heat flow), the following effects occur:
- Second Ettingshausen-Nernst effect : a potential difference (electrical voltage) in the longitudinal direction.
- Maggi-Righi-Leduc effect (also known as the second Righi-Leduc effect ): a change in thermal conductivity in the longitudinal direction, combined with a temperature difference.
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.
Related effects
Galvanomagnetic effects occur when a magnetic field acts on an electric current. In this case, one also observes transverse and longitudinal potential and temperature differences. A prominent example is the Hall effect .
In thermoelectricity , the generation of a potential difference with a heat flow and the generation of a heat flow with a potential difference are considered (without a magnetic field).
literature
- Ekbert Hering, Rolf Martin, Martin Stohrer: Physics for engineers. Springer, 10th edition 2007, pp. 845f
- Horst Teichmann: Applied Electronics , Vol. 1: Electronic line, electron optics , University pocket books 343, Springer-Verlag, 1974, ISBN 978-3-7985-0397-7 , pp. 27f