Faraday's Law of Electrolysis :-

     (a)  The mass of a substance produced by a cathode or anode reaction in electrolysis

directly proportional to the quantity of electricity ( i.e. charge ) passed through the cell.

     (b)  The masses of different substances produced by the same quantity of electricity are proportional to the equivalent weight  of the two substances.

Electrolysis of water | Faraday's Laws of Electrolysis