Voltage generator using a magnetic fluid
Résumé
We describe the concept of a voltage generator based on the use of a magnetic fluid. A cell contains two immiscible liquids: the lower liquid boils at a low temperature and the upper is a magnetic liquid magnetized by a permanent magnet. By heating the bottom of the cell the lower liquid boils, and bubbles of the gas phase cross both liquid phases; consequently a flux variation is induced in a detection coil. Finally, the gas phase condenses in a recovery device in order to be injected back at the bottom of the cell. We obtain a voltage generator with a shape signal linked to the nucleation frequency and volume of the gas bubbles. This device has been built by secondary school pupils and requires the acquisition of knowledge of magnetism, hydrodynamics and thermodynamics.