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Most fruits and vegetables contains juice that to some degree is acidic. The juice from these fruits or vegetable is a solution (electrolytes) containing ions that will transfer electrons and therefore generate electricity. If metal electrodes such as copper and zinc are inserted into the solution, electrons will travel from the anode (zinc) which readily accept electrons to the cathode (copper) which readily donate electrons, producing an electric current. The cathode has a positive charge and the anode has a negative charge. Fruits such as lemon and orange which are more acidic than most other fruits make better batteries because they produce more electrons and therefore more electric current.
■ Split the potato into two equal parts
■ Connect the alligator clips and the connecting wires together
■ Insert the a copper and a zinc strip into each of the potato sections and connect the two sections in series. That is, use a connecting wire with an alligator clip to connect the netative terminal of one section to the positive terminal of the other section
■ Connect the watch to the free positive copper electrode and the negative free zinc electrode
■ The two potato batteries in series generates enouge electricity capable of powering the digital watch.
■ Observe how the digital watch runs immidiately as the circuit is closed up. That is it! you have just made your first potato battery.
The video below will show you how to carry out this project