https://www.youtube.com/watch?v=R9a2oZXT2nw&t=47s (https://www.youtube.com/watch?v=R9a2oZXT2nw&t=47s)
Lemon battery. 1 lemon Generates 1 volt and 0.003 amperes.
Electrodes made from copper and zinc. Experiment for children. For training in electrical engineering