Physics Lab Activity
Electrostatics - 3
Induction & Polarization
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Purpose:
* to observe, describe and explain induction and charging by
induction.
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:
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plastic strips
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cloth scraps
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pith ball with thread
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ring stand
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ring stand clamp
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electroscope
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Styrofoam "peanuts" or a balloon
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empty "soda pop" can
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tape
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Description:
Part 1 - Charging by Induction
Follow steps 1 - 4 to charge your electroscope by
induction:
- Ground the electroscope by touching the top plate with your
finger.
- Bring a charged strip near the top plate of the electroscope,
but not touching it.
- Ground the electroscope by touching the top plate with your
finger. Be sure that the charged strip is held near (but not
touching) the electroscope's top plate while you do this.
- After removing your finger from the electroscope,
remove the charged rod from near the electroscope's top
plate.
- How do you know that the electroscope has an electric charge
after completing step 4?
- Is the charge on the electroscope the same as the charge on
the charged strip, or opposite? (Don't just guess - test it!) How
do you know?
- Write a description of what happens to the electric charges on
the electroscope when you follow steps 1 - 4.
Part 2 - Electrical Polarization
- Lay an empty "pop" can on its side on your lab table. Bring
your charged strip near the can but not touching it.
Describe what happens. Why does this happen?
- Hang a pith ball and observe what happens when a charged strip
is brought near the neutral pith ball. (You did this
in the first electrostatics lab.) What happens, and
why?
- Get some Styrofoam peanuts (or a balloon - be careful blowing
it up!). Note that they stick easily to the wall (and you!) after
charging. Why?
last update February 14, 2001 by JL
Stanbrough