5A10.35 - Tape - Equal and Opposite Charges

Code Number:
5A10.35
Demo Title:
Tape - Equal and Opposite Charges
Condition:
Good
Principle:
Electrostatics
Area of Study:
Electricity & Magnetism
Equipment:
Tape, Pasco Electrometer with Cage, and Flat Metal Plate.
Procedure:

Place 2 pieces of tape on top of each other on the metal plate and rub firmly.  It will help if you label the top tape with a T and the bottom tape with a B.  Remove both pieces from the metal and then separate.  The bottom piece should have negative charges and the top piece should have a positive charge.

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.

References:
• Xueli Zou, "Conductors and Insulators: A QuickTime Movie", TPT, Vol. 43, #7, Oct. 2005, p. 460.
• Randal Harrington, "Getting a Charge Out of Transparent Tape", TPT, Vol. 38, #1, Jan. 2000, p. 23.
• Alan Van Heuvelen, Leith Allen, and Pavlos Mihas, "Experiment Problems for Electricity and Magnetism", TPT, Vol. 37, #8, Nov. 1999, p. 482.
• J. Harris and A. Ahlgren, "Some Simple Experiments and Demonstrations", TPT, Vol. 4, #7, Oct. 1966, p. 314.
• Robert A. Morse, "Laboratory Activity 1: Separating Charges & Forces Between Charged Objects", Teaching about Electrostatics, p. 3-1.
• Pat Murphy, Ellen Macaulay, and the staff of the Exploratorium, "Charge It!", Exploratopia, p. 325.
• Borislaw Bilash II and David Maiullo, "It's Always Negative", A Demo a Day: A Year of Physics Demonstrations, p. 243.
• Janice VanCleave, "67, Are You Attractive?", Teaching the Fun of Physics, p. 103.
• Bobby Mercer, "Tape Repulsion", Junk Drawer Chemistry, 2016, p. 71 - 74.
• Grant Mellor, "5. The Nature of Neutral", Flying Tinsel, 1993, p. 25 - 27.
• Grant Mellor, "4. An Unexpected Reaction", Flying Tinsel, 1993, p. 20 - 24.
• Rudolf F. Graf, "Like Charges Repel ", Safe and Simple Electrical Experiments, p. 10.
• Rudolf F. Graf, "The Charged Tape", Safe and Simple Electrical Experiments, p. 34.

Disclaimer: These demonstrations are provided only for illustrative use by persons affiliated with The University of Iowa and only under the direction of a trained instructor or physicist.  The University of Iowa is not responsible for demonstrations performed by those using their own equipment or who choose to use this reference material for their own purpose.  The demonstrations included here are within the public domain and can be found in materials contained in libraries, bookstores, and through electronic sources.  Performing all or any portion of any of these demonstrations, with or without revisions not depicted here entails inherent risks.  These risks include, without limitation, bodily injury (and possibly death), including risks to health that may be temporary or permanent and that may exacerbate a pre-existing medical condition; and property loss or damage.  Anyone performing any part of these demonstrations, even with revisions, knowingly and voluntarily assumes all risks associated with them.