Battery with potatoes

Electrochemical cells are based on the process of electron flow in a system with varying potential differences. Batteries are composed of such systems and contain different chemicals for different purposes and price ranges. You can make simple experimental batteries using metal wires and items such as lemons, apples, and potatoes. What are some other homemade battery sources, and what is the role of these food items in producing electrical energy that can be measured as battery power Explain your answers. 

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