I was watching a video https://www.youtube.com/watch?v=uvT3XvDSSQw about piezoelectric materials.
They mentioned that "a current can flow when a pressure is applied to the material".
I have a problem with this expression. I'm not sure if my confusion is in its place.
I know that when a stress is applied on a piezoelectric material, it will generate an electric field due to the dislocation of the electric charges/ creation of electric dipoles.
But that doesn't mean that a current should flow from the material, because if a current flows, that means the material has lost electrons, therefore has lost some mass.
And in case it was true that the electrons were leaving the material instead of just emitting their electric field while still being connected with the materials molecules, then I think what they mentioned about connecting the material to a circuit and measuring the current flow will make sense.