Why electrochemical cell stops working after sometimes ?

Explanation

In a galvanic cell, electrons flow from the electrode at a lower reduction potential (i.e., anode) to an electrode at a higher reduction potential (i.e., cathode). When the current is drawn from a cell, the concentration of cations in the oxidation half cell (i.e., anode) increases while the concentration of cations concentration of ions in solution, the reduction potential of anode start increasing, whereas reduction potential of cathode start decreasing. As e.m.f. of cell is given by the expression,

e.m.f of the cell gradually decreases with time. ultimately a stage is reached when the `E_("cathode")` and `E_("anode")` becomes equal and cell stops working.