When you run out of batteries , but you have a few lemons at home (: To make our own electricity we put copper coins and galvanised nails on different sides of lemons . Then we connected the nail to the copper coin on the next lemon in a line with a wire . After connecting red wire (representing " + " ) to the coin on the first lemon and black wire (representing " - " ) to the nail of the last lemon , it wa . . .