an effect后面加介词on，an effect on中文意思是n. 作用，影响（刻意制造的）效果，印象所有物，财产生效，实行

Her words had a magical effect on us.她的话对我们有一种魔力般的作用。

His voice had an almost hypnotic effect.她的话对我们有一种魔力般的作用。