PART 1 - In collaboration with Jacques Curie, these experiments provided confirmation of a phenomenon predicted by Gabriel Lippmann: the electrical expansion of quartz.

When a compressive force is applied along the electric axis of a quartz crystal, an electrical charge proportional to the force is produced, q=Kfq = Kfq=Kf. Conversely, when a potential difference is applied across the same faces, the crystal undergoes a mechanical deformation proportional to the applied voltage, δ=KV\delta = KVδ=KV.

This reciprocity establishes a direct relationship between mechanical and electrical effects, showing that the deformation of quartz is governed by its electrical state and by the symmetry of its crystalline structure.