The Physics
Hypertextbook
Opus in profectus

# Electric Charge

## Problems

### practice

1. Write something.
2. Write something.
3. Write something.
4. Write something completely different.

### conceptual

1. Explain how an object that is electrically charged (like a balloon after it has been rubbed on hair) can be attracted to an object that is electrically neutral (like a wall in your home or classroom).
2. Describe a procedure that could be used to determine the sign of the charge on an object.
3. You and three of your friends are playing golf on a seemingly fine afternoon when, of course, it begins to rain. A bolt of lightning strikes one of your friends who is motionless and unresponsive. When will your friend be "safe" enough to touch so that you can render first aid without electrocuting yourself?
4. Two related questions.
1. Why should you touch your finger to the metal portions of the case of a computer before you open it to insert or replace parts?
2. Why should you place empty fuel cans on the ground before filling them with gasoline, kerosene, diesel, etc.?
5. electroscope-hand.pdf
With the aid of diagrams, show the distribution of charges on an electroscope and the position of its leaves during the following experiment.
1. Take an uncharged electroscope and place your finger on the terminal.
2. Bring a negatively charged rod near the terminal.
3. Move your finger and the charged rod away from the terminal at the same time. What is the charge on the electroscope?
4. Repeat the procedure described above, but replace the negatively charged rod with one that is positively charged.
6. With the aid of diagrams, show the distribution of charges on two identical uncharged metal spheres in contact during the following experiment.
1. Bring a positively charged rod near one of the spheres on the side opposite the point of contact.
2. Separate the two spheres and remove the rod. What charge does each sphere have?
3. Touch the two spheres together. What charge does each have?
4. Repeat the procedure described above, but replace the positively charged rod with one that is negatively charged.
7. electroscope.pdf
With the aid of diagrams, show the distribution of charges on an electroscope and the position of its leaves for each of the following scenarios.
Eight experiments with an electroscope
initial charge
of electroscope
charge on rod position of rod
relative to terminal
a. uncharged positive in contact, then removed
b. uncharged negative in contact, then removed
c. uncharged positive near, but not in contact
d. uncharged negative near, but not in contact
e. positive positive near, but not in contact
f. positive negative near, but not in contact
g. negative positive near, but not in contact
h. negative negative near, but not in contact