Zinc and copper annodes are hooked to positive and negative terminals of a small electronic clock. A fruit or vegetable is pierced by the annodes and the acid inside serves as battery acid. Think phosporic acid (potato) citric acid (lemon), the acid in tomatoes and etc. Cool, especially if you don't tell the kiddos about the physics and hook up a candy bar to show how the clock doesn't run - must be a bad food with no energy.
Here's a picture - http://www.kidsgardeningstore.com/22-1053.html
Originally Posted by lisa tberry
okay, I gotta know what is a potato clock?
For me it's SUNGLASSES, and my highlighter to map my daily activities.