A rotating one of these is used in a dynamo to  generate electricity, and, according to Gauss's Law, it cannot have monopoles.
The Faraday rotation studies the interaction of light and this in a medium, and it induces a  quantized resistivity in the quantum Hall effect. A rotating one of these is used in a dynamo to  generate electricity, and, according to Gauss's Law, it cannot have monopoles. It generates the  Lorentz force on moving charged particles, and it can be calculated with the Biot-Savart Law.  The Earth's one can reverse itself, and the SI unit for it is the tesla. For 10 points, identify this  entity, caused by a moving point charge that is the counterpart of an electric field and has poles.
The Faraday rotation studies the interaction of light and this in a medium, and it induces a  quantized resistivity in the quantum Hall effect.
{magnetic fields} [prompt on “field”, do not accept or prompt on “electric field”]