Problem Set 2.1:       Forces on Charged Objects (Informal Lab)

 

Instructions:

Follow the instructions for the mini-lab and answer the questions that follow. Complete the question. Keep this assignment in your portfolio.

Do electric charges interact?

Instructions:

Take a roll of removable clear cellophane tape (Scotch tape). Fold over about 5 mm on the end of the tape for a handle. Then tear off a strip 8 to 10 cm long. Stick the strip on a dry, smooth surface, such as your desktop. Make a second strip of tape in the same way and stick it on top of the first tape.

  1. Now quickly pull both pieces off the desk and pull them apart. Then bring the tapes close together.*
  2. Now make two new strips of tape (or use the same ones), but this time press each one onto the desk separately. Then pull them off and bring the two strips close together.*

* You may have to try these a few times to get the desired effect. There should be an attraction or repulsion of the tape pieces if the technique is done correctly. Do not let the pieces of tape ground out by touching them to any objects.

Questions:

1.     What happened when you brought the first pair of tapes close together?

                                                                                                                                                           attract

2.     What happened when you brought the second pair together?

                                                                                                                                                              repel

3.     What did you do that might have caused the two different reactions?

        Ripping apart the pieces of tape or removing them from the table causes charges to separate

                       Ripping them apart caused different charges, other setting caused the same charge

4.     Did the second pair of tapes push apart more when they were closer together or farther apart?

                                                                                                      More when they were closer together

5.     When was the force between them stronger?                                                When they were the closest

6.     In terms of subatomic particles (protons, neutrons, electrons), explain how these strips became electrically charged?

                                                                 Electrons are transferred from one piece of tape to another

                                                                                                       This causes them to become charged

 

Check Your Understanding

1. As you move two charged cello tapes closer together, do the forces between them become greater or smaller?

2. If you rub hard rubber with a piece of wool, what charge is on the rubber?

3. APPLY: Explain why, after combing, your hair is sometimes attracted to your comb.