
When electric current is passed through acidulated water , then it split into hydrogen and oxygen molecule that is H2 and O2 
Chemical equation for above reaction :-
2H20 on electrolysis given 2H2 + O2 
This spilliting of water  due to electricity is called electrolysis .
In electrolysis,  H2 moves towards cathode as it forms positive ions whereas O2 moves towards anode as it forms negative ions .