At-Home Activity on Electricity (solutions)

Feel free to work on the homework in groups. The work you hand in, however, should reflect your understanding of the material and be in your own words.Students who turn in identical (or close to identical) homework assignments will be asked to explain their answers orally to the TA or prof. A student who cannot explain how he or she arrived at a given answer will be charged with academic dishonesty.

You should show all of your calculations (neatly) and justify all of your answers for full credit.

The Electricity of Scotch Tape

Take a piece of cellophane tape about a foot long and stick it to your desk. Lift up one end of the tape carefully, then quickly pull up on that end to remove the tape from the desk. This will charge the piece of tape. If you do not see any attraction or repulsion of the tape in the following activities, try a new piece of tape or a different roll of tape. Now bring the tape close to the desk without letting it touch the desk.

1.	What happens when you do this? What if you bring the tape close to a person? Close to your chair? Does this effect depend on which side of the tape is closest to the object? Should see attraction to all objects, regardless of which side is closer.

Repeat the procedure and charge another piece of tape.

2. Does this piece behave the same as the other piece of tape? What happens if you bring the two pieces of tape close (don't let them touch!)?
Should behave the same. The two pieces of tape should repel each other.

3. Does the effect increase or decrease as you decrease the distance between the two pieces of tape?
The effect should increase as the pieces get closer to each other.

4. Do you think the two pieces have the same electric charge or different charges? Why?
Same charge because you did the same thing to both of them. The fact that they repel confirms this.

Now stick a new piece of tape to the desk and leave it there. Stick another piece on top of it. Quickly remove BOTH pieces, leaving them stuck together.

5. Does this double piece act like the original piece of tape?
Yes, it should.

Pull the two pieces of tape apart, and examine their behavior when you bring them close to the table.

6. Do they behave similarly or differently when you bring them close to the table?
They should behave similarly.

7. What happens when you bring each of them close to the original piece of tape? Do they behave similarly or differently?
Differently. One is attracted, one is repelled.

8. Describe what happens when you bring them close to each other.
They are attracted to each other.

9. Do you think the two pieces have the same electric charge or different charges? Why?
Different, because they attract.

2.	Does this piece behave the same as the other piece of tape? What happens if you bring the two pieces of tape close (don't let them touch!)? Should behave the same. The two pieces of tape should repel each other.
3.	Does the effect increase or decrease as you decrease the distance between the two pieces of tape? The effect should increase as the pieces get closer to each other.
4.	Do you think the two pieces have the same electric charge or different charges? Why? Same charge because you did the same thing to both of them. The fact that they repel confirms this.

6.	Do they behave similarly or differently when you bring them close to the table? They should behave similarly.
7.	What happens when you bring each of them close to the original piece of tape? Do they behave similarly or differently? Differently. One is attracted, one is repelled.
8.	Describe what happens when you bring them close to each other. They are attracted to each other.
9.	Do you think the two pieces have the same electric charge or different charges? Why? Different, because they attract.