Tangible: Charged Tape
Purpose
You will use Scotch tape to investigate the nature of electrical interactions.
By the end of this lab, you will be able to
-
predict whether two objects will attract or repel each other or have no
electrical interaction
-
describe how distance affects the strength of electrical interactions
Procedure
Keep careful lab notes
of your procedures, predictions, observations and answers to questions.
This lab has two parts. Start with Part 1.
Questions
Put the answers to these questions in your lab
notes.
Observations of Charged Tape
Procedure for Part 1:
Press a piece of tape about 15 cm long onto a smooth unpainted surface
(the table or a notebook will work). For ease in handling, make "handles"
by folding back one end of the tape, as shown below. Then peel the tape
off the surface and hang it from the side of the table. Describe the behavior
of the tape as you bring objects (e.g. your hand, a pen) near the it.
Prepare another tape identical to the first one using the procedure
described above.
-
Describe your observations as you bring the second tape near the first.
-
Describe how the distance between the tapes affects the interaction between
them.
Run the second tape through your fingers several times. Describe your observations
as you bring objects near the second tape (the one you ran your fingers
over).
STOP! Check your observations with other groups at your table
before going on to Part 2:
Charged Tape
Procedure for Part 2:
Stick a tape with a handle to the table and write "B" (for bottom) on it.
Then press another tape with a handle down on top of the "B" tape and label
it "T" (for top). Pull the pair of tapes off the table as a unit. Run your
fingers over the pair of tapes. Now pull them apart and hang them from
the side of the table. Predict the interaction between the following pairs
of objects. Record your predictions in a table like the one below.
|
Prediction |
Observation |
| two T tapes |
|
|
| two B tapes |
|
|
| a T tape and a B tape |
|
|
| a T tape and your hand |
|
|
| a B tape and your hand |
|
|
Prepare another set of "B" and "T" tapes and test your predictions.
Record your observations. If any of your observations do not match your
predictions, resolve any inconsistencies. Check your observations for Part
2 with other groups at your your table before going on to the questions.
Charged Tape
Questions
-
What does rubbing the tape with your fingers do? What observations support
this conclusion?
-
Which objects (if any) are attracted to both the T tape and the
B tape? How is this possible?
-
When a certain unknown tape is brought near a T tape, the two tapes
repel each other. What would happen if the unknown tape was brought near
a B tape? Explain your reasoning.
-
When a different unknown tape is brought near a T tape, the two
tapes attract each other. What would happen if this unknown tape was brought
near a B tape? Can you be sure of your answer? Explain your reasoning.
-
Using only the information gathered in this lab, can you tell which tape
is "negatively charged"? If so, explain how you can tell. If not, explain
what test you could perform to conclusively determine which tape is "negatively
charged."