My chem teacher is having trouble explaining the a particular happening in a fuel cell to the class. In a galvanic cell +ve ions move towards the +ve electrode and -ve to the -ve. In electrolytic cells the +ve ions move towards the -ve electrode and -ve to the +ve. He says that the reason why it is opposite in electrolytic cells is because it is being forced by the battery to do the opposite, but he is at a loss as to how to explain why +ve ions move towards +ve electrodes in the "natural" situations (ie. not being forced). Any help with how to describe why this happens will be much appreciated.