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If the zinc is connected by means of a wire, W, with a strip of copper, C, dipping in the same solution, the zinc will still to continue to dissolve but the hydrogen bubbles will now form on the surface of the copper strip as well as on the zinc. It will be found that the wire W becomes heated. If the copper and zinc are connected to a galvanometer it will show the presence of an electric current passing through the circuit. The cell may be considered as a sort of chemical furnace in which fuel is burned to drive the current. The zinc is the fuel. The copper is merely present to "pick up" the current and takes no part chemically.

If a number of such simple cells are properly united, the zinc of one being joined to the copper of the next and so on, a battery is formed. The current flows from the copper, called the positive pole, through the wires (when they are joined) to the zinc or negative pole and back to the copper through the solution.

The electricity generated by the cells exerts a certain pressure or tendency to pass through the wires. This tendency is called the potential. The potential is measured in volts. The potential (also called the electromotive force) in the case of the Voltaic Cell just described is 1.07 volts. If the copper strip is replaced with one of graphite or carbon, the voltage will rise to 1.73 volts.