Continuos flow of charges: electric current
Flow of charges between two regions with opposite net charges
electrons (negative charges) flow from the lower electrical potential points to ones with higher electric potential
positive charges flow from points with higher electric potential to points with lower electric potential
result of flow --> annihilation of charges
to maintain a constant flow, one must maintain a constant potential difference: constant tension
use of a Van der Graff generator (we invest mechanical energy to get electric energy)
use of batteries (we invest chemical energy)