# Dresden 2017 – wissenschaftliches Programm

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# DD: Fachverband Didaktik der Physik

## DD 8: Hochschuldidaktik 2

### DD 8.4: Vortrag

### Montag, 20. März 2017, 18:40–19:00, GER 52

**Induced voltage in an open wire** — •Klaus Morawetz^{1,2,3}, Markus Gilbert^{1}, and Andreas Trupp^{4} — ^{1}Münster University of Applied Sciences,Stegerwaldstrasse 39, 48565 Steinfurt, Germany — ^{2}International Institute of Physics (IIP)Av. Odilon Gomes de Lima 1722, 59078-400 Natal, Brazil — ^{3}Max-Planck-Institute for the Physics of Complex Systems, 01187 Dresden, Germany — ^{4}Brandenburg University of Applied Police Sciences, Bernauer Straße 146,16515 Oranienburg, Germany

A puzzle arising from Faraday’s law is considered and solved concerning the question which voltage is induced in an open wire with a time-varying homogeneous magnetic field. Integrating the electric field along the wire, it is found that the longitudinal electric field with respect to the wave vector contributes with 1/3 and the transverse field with 2/3 to the induced voltage. In order to find the electric fields the sources of the magnetic fields are necessary to know. The representation of a spatially homogeneous and time-varying magnetic field implies unavoidably a certain symmetry point or symmetry line which both depend on the geometry of the source. As a consequence, the induced voltage of an open wire is found to be the area covered with respect to this symmetry line or point perpendicular to the magnetic field. This in turn allows to find the symmetry points of a magnetic field source by measuring the voltage of an open wire placed with different angles in the magnetic field. We present four exactly solvable models of Maxwell’s equation illustrating different symmetries.