An iPhone Powered By Oranges
One form of energy can be converted into another. For example, the energy stored in a piece of food can be converted into energy that helps you grow and move. The energy stored in certain kinds of food can also be converted into electricity. A piece of fruit such as a banana, pineapple or orange can produce voltage when electrodes made of different metals (copper & zinc) are placed into the fruit.
Imperial Leisure, a UK social marketing/advertising agency, created a unique marketing campaign to promote Jaffa oranges (similar to the Valencia orange, but sweeter). 2380 orange slices from 750 oranges were used to charge an iPhone.