Physics Lab Activity
Electrostatics 1
Charging by Friction & Contact
Purpose:
* to observe, describe and explain:
- charging by friction and contact
- evidence for two kinds of electrical charge
Note: You may work with one
or two partners for this activity. Discuss the explanations and
answers with your partner(s) and write one clear, accurate answer
on another sheet of paper. Be sure that all participants put
their name on this sheet.
Equipment:
plastic strips
|
cloth scraps
|
2 pith balls with thread
|
ring stand
|
ring stand clamp
|
tape
|
Description:
Part 1 - A Single Pith Ball
- Hang a single pith ball from a ring stand clamp using a small
piece of tape.
- Charge a plastic strip by rubbing with a cloth scrap.
- Bring the charged strip close to but not
touching the pith ball. Describe what happens.
- Allow the pith ball to touch the charged strip. What happens
now? Why does the pith ball do that?
- After you touch the pith ball with your hand, how does it
behave? Why?
- Devise a test to tell whether your plastic strip has a
positive or a negative charge and write a short description. (You
may borrow a plastic rod and fur pad or glass rod and silk cloth
from your teacher for this test.) Carry out your test. Is the
plastic strip positively or negatively charged?
- See if you can find a combination of plastic strip and cloth
that will produce the opposite charge from your original strip.
(You may use your own object, such as a comb, etc. if you wish.)
How do you know that it is oppositely charged?
Part 2 - Two Pith Balls
- Hang a second pith ball next to your original so that they are
touching when they are at rest.
- Charge both pith balls with your plastic strip. What happens?
Why?
- If you bring the charged strip close to the two charged pith
balls without touching them, what happens? Why?
- If you bring an oppositely-charged strip near the charged pith
balls without touching them, what happens? Why?
Click here to check your
answers.
last update February 14, 2001 by JL
Stanbrough