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..

Two negatively charged pieces of tape can be made by placing two pieces of tape on a table top, but not on top of each other.  When pulled quickly off the table, each piece will have a negative charge. 

Place up to 7 pieces of tape, 4 cm long, on top of each other on the metal plate without rubbing.  Carefully pull the tape pile off of the metal plate and neutralize any excess charge with water.  Pull the top piece of tape off of the pile and measure its charge (this should be positive).  Pull off the next piece and show that is also has a positive charge of equal value.  This should continue until the last piece is removed at which time it will be found that the bottom piece has a negative charge equal to the combined charge of the top 6 pieces.