Question

explain how an electric cell maintain a constant ppotential difference

Answer 1

Electric cell do not actually maintain a constant potential, its potential falls with use. However it provides nearly constant potential.

Inside the cell there occurs chemical reaction, these reactions create the difference of potential across the terminals of the cell.  Now the reactions occur nearly at constant rate so it maintains nearly constant potential difference.

Answer 2

Hey dear!!

Ab electric cell or a battery manitains potential difference across the ends of a conductor.
The chemical action within the cell generates the difference in the potential between the electrodes which are connected with the two ends of the conductor.

Hope this helps you dear ✌✌✌