Demonstrations

Potato Clock

Code Number :	5E40.27?
Disclaimer:	Reprinted by permission of Dick Berg, University of Maryland, for use on this website. The demonstrations contained and referenced herein are listed for the purposes of cataloging and describing physics demonstrations which should be conducted only under the direction of a trained instructional support professional or physicist. These demonstrations are not presented for the purpose of being conducted by persons unconnected to this Facility and/or persons not consulting with or being supervised by the recognized instructional support professional or physicist and his/her staff. The University is responsible only for those demonstrations carried out using its own equipment using established safety and scheduling policies, and bears no responsibility for those choosing to use this source material for their own purposes. All demonstrations described and contained herein are public domain, and can also be found in reference materials in libraries, bookstores, and electronic sources. Further information regarding legal liability in use of demonstrations and labs will be found on the web site Injuries in School/College Laboratories in USA. The University of Iowa Disclaimers: University of Iowa Disclaimer All Rights Reserved..
Condition :	Excellent
Principle :	Electrode Materials in Acid Solutions
Area of Study :	Electricity & Magnetism
Equipment :	Potato Clock with Electrodes, Coke clock with electrodes, Two 50 ml Beakers, Fruits and Vegetables - Lemons; Potatoes; Oranges; Grapefruit; Etc., Two Potted Plants, Soda Pop (Mountain Dew).
Procedure :	This unit is designed to show that a battery may be made from a acidic fluid or fluid matrix and two electrodes of different materials, in this case copper and zinc. These clocks runs on approximately 2 to 3 volts so the unit has two cells connected in series. Usually I use two small beakers filled with Mountain Dew. Insert a copper and zinc electrode into each beaker making sure that electrodes do not touch each other. The clock should start immediately and can then be set to the correct time. The two beakers may be replaced with two potatoes, two lemons, two potted plants, and a host of other possibilities. In the fluid matrix situations ( fruits and plants ) the electrodes may have to be moved to within 1/2 inch of each other to maintain the needed conductivity.

References

James Stankevitz, Roy Coleman, "A Curious Clock", TPT, Vol. 23, # 4, Apr. 1985, p. 242 - 244.

Janice VanCleave, "Potato Circuit," Physics for Every Kid - 101 Easy Experiments in Motion, Heat, Light, Machines, and Sound, p. 16 - 17.

Mail Questions and Comments to: Dale Stille