A simple voltaic cell is made by immersing one zinc plate and one copper plate inside a water diluted sulfuric acid solution. As shown in the figure, if the copper plate and zinc plate are connected externally with an electrical load, an electric current starts flowing from copper plate to zinc plate through the load. That means there is some electrical potential difference developed between the copper plate and the zinc plate. As the current flows from copper to zinc, it is obvious that the cop