Name _______________________________ # _______ Section_________

  

 STATIC ELECTRICITY
 REGENTS RULES – Full Sentences for FULL CREDIT

 

Static electricity consists of charges trapped in a body moving randomly.

In order to understand static electricity we need to know three principles:

 

  1. ______________________________________2. ______________________

 

  3. ______________________________________
 

Neutral objects become positive by ___________    ______________

 

Neutral objects become negative by _________________     ________________

 

In this experiment we will be charging:

 

·        black rubber rods are charged with _________________- BLACK ROD becomes negative

 

·        And glass rods are charged with _________________  - GLASS ROD becomes positive

 

We will also being using pith balls in this lab. These pith balls have a styrofoam center with a coating of metallic paint. The pith ball is suspended by a silk thread, which keeps the pith ball from being grounded.

 Before contact pith ball is neutral

Show the charge arrangement in the pith ball when the negative rod comes near.

 

What happens when the rod touches the pith ball? _________________________________________

Objective

During this investigation you will use pith balls and an electroscope to investigate some behaviors of static charges.

 

 

a) What is the purpose of the white plastic collar on the electroscope?

 

 

 

b) Label the leaves of the electroscope shown on the left.

 

 

 

Procedure

A. Charging a Pith Ball

 

1.  Rub the rubber rod with wool. SLOWLY bring the rod close to a suspended pith ball.

 

Explain why the pith ball is first attracted to the rod and then repelled by it.

 

__________________________________________________

 

 

 

2. What would the final charge on the pith be if you used a positive charged rod and followed the same procedure as before?

 

Explain ____________________________________________________

 

__________________________________________________________

 

B. Charging the Electroscope by Conduction

 

Rubber Rod - Conduction

 

Charge the rubber rod by rubbing it with wool. Touch the rubber rod to the top of the electroscope.

 

a)When the rod is removed, what is the charge of the electroscope? ________________

 

b)    What kind of charge moved between the rod and electroscope to give the electroscope that charge? 

 

 

c) In which direction did the charge move? __________________________________

 

____________________________________________________________________

 

d)     What rule of static electricity do the leaves of the electroscope diverge?

 

      ______________________________________________________________

 

e)     Why do the leaves remain diverged, even when the rod is pulled away?

 

________________________________________________________________

 

 

f) Touch the top of the electroscope with your finger.

 

Where did the electrons move to make the electroscope neutral?

 

______________________________________________________________

 

GLASS ROD - Conduction

Charge the glass rod by rubbing it with silk. Touch the glass rod to the top of the electroscope. (KEEP TRYING UNTIL THE LEAVES FINALLY DIVERGE)

 

a)     What is the charge of the electroscope? ________________

 

b)     What kind of charge moved between the rod and electroscope to give the electroscope that charge?

 

 

 

 

c) In which direction did the charge move? __________________________________

 

____________________________________________________________________

 

d) What rule of static electricity explains why the leaves of the electroscope diverge?

 

      ______________________________________________________________

 

e) Why do the leaves remain diverged, even when the rod is pulled away?

 

________________________________________________________________

 

 f) Touch the top of the electroscope with your finger. Where did the electrons move to make the electroscope neutral?

 

______________________________________________________________

 

Summarize your observations involving charging the electroscope by conduction.

 

 

 

D. Charging the Electroscope by induction

 

1.  Bring a negatively charged rod (BLACK) NEAR but not touching the electroscope.

2.  Remove the rod.

3.  Again bring the charged rod near the electroscope. With the rod still close, briefly touch your finger to the electroscope. With the rod still held close, remove your finger.

4.   Now remove the charged rod.

5.   Test the charge on the electroscope by bringing a negatively charged rod near the electroscope.

What is the charge of the electroscope?          ____________________

 

6. Explain why the electroscope has this charge.

 

 

7. What would the charge of the electroscope be if you used a positive rod in this last experiment?

 

 

 

8. Explain why the electroscope would have this charge if you used a positively charged rod.

 

 

 

9. Compared with the charging body, what is the charge on an electroscope when it is charged by

 

conduction? _________________________ (Answer “The same “ or “ Different”)

 

induction? ___________________________ (Answer “The same “ or “Different”)

 

10. Ball A and B below start out neutral. A negatively charged rod is brought near the two spheres and then ball B is moved away.  The charged rod is removed. What charges do you think will exist on Ball A and B? Explain.