A.C.can not be used for electrolysis.why?

Hi @Zaiba .In electrolysis the ionisation of the electrolyte takes place where the positive and negative charges move towards opposite electrodes.For this the electrodes are required to be maintained at opp. polarity as long as the process continues which is possible while supplying a dc current.But if we pass an ac current the polarity of the electrodes will be continuously changing and the ions will not be attracted toward any particular electrode resulting in no ionisation.Hence electrolysis cannot take place with ac current.
hope it helps...