I was trying to create some redstone stuff and i knew hoppers would collect items when it was powered, but not send them. But they only take items sended by hoppers. If you try to throw a item at the hopper the item will just start jumping and not going in the hopper. Same with sending from chest and minecart with hopper. If it is supposed to not go in when powered, then fix so hoppers wont send in powered hoppers.