Electrolytic cell:

Consider the electrolytic cell display in Figure. A voltage E_applied is applied to the cell in like a way that a current flows by the cell.  While E_applied > Ec_ell, there will be a flow of current in the circuit.  While there is a current, the potential of the cell is less than the thermodynamic potential since one or one of the following phenomena is operating:  IR drop, concentration polarisation and kinetic (chemical)   polarisation.

Figure: An electrolytic cell