Question

1)DC is preferred than AC in electroplating .why?
2)AC cannot be use for electrolysis. why?

Answer 1

DC is preferred than AC in electroplating b'coz 2 produce radio waves for domestic supply for electronics 

Answer 2

Both the questions seem to be interconnected (:P). You can write the same answer for both the questions (:D ).

DC is preferred over AC b'coz, in DC , the direction of the current is constant and hence the polarity remains constant, whereas in AC the direction of the current keeps changing periodically and hence the polarity of the battery keeps changing making it difficult for electroplating.