Q1: Describe and sketch the interaction. Does the strength of the interaction change with the distance between tapes?

The ends of the tape repel each other. The closer the two pieces, the stronger the force of repulsion.

Q2: Describe and sketch the interaction between your bottom and top piece. Does it depend on distance between the tapes, and if so how? 

The ends of the tape attract each other. The closer the two pieces, the stronger the force of attraction.

All tops repel other tops. All bottoms repel other bottoms. All tops attract all bottoms.

The interactions described in Q3 can be classified into two types of behavior; "top" behavior and "bottom" behavior. This supports the claim that there are two types of charges giving rise to the two different behaviors.

Q5: Account for these phenomena using the 'electron fluid' model of charge behavior by sketching diagrams of the pieces of tape with charges in your report. Describe in words what tape has what charge and where it came from. 

Under the "electron fluid" model electrons flow from one piece of tape to the other while they are being pulled apart. The tape with more "electron fluid" at the end is negatively charged. The piece that lost the "fluid" is positively charged.

Q6: Describe the interaction between your bottom and top tapes in terms of conservation of charge.

As the tape is pulled apart the original number of movable charged particles (presumably electrons) are unevenly distributed between the pieces of tape. No net charge is created in the process. If the pieces were originally neutral, the tape with more electrons will be negatively charged and the tape with fewer will be positively charged. The magnitude of the positive and negative charge will be the same. Therefore the sum of the final charges will equal the initial charge (in this case neutral).

Q7: Invent and describe a test for a third type of charge. Try it. Describe and interpret your results. 

Advanced Question 1: Can you sketch and describe an experiment which could (very crudely) determine the number of excess electrons on a piece of charged tape? Sketch your experiment. Here are some hints:

• a 1 half-inch (1.2 cm) wide piece of tape 20 cm long has a mass of about 0.16 g
• for a crude approximation you could replace a strip of tape by a small charged ball or 'point charge' on a massless string and draw a free body diagram of the sphere
• e = 1.6 x 10-19 C
• Newton's second law applies here
• You have to use some trigonometry (what are typical angles and distances?)