Electrostatics practice test
Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
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1. An attracting force occurs between two charged objects when the charges are of
a. unlike signs.
c. equal magnitude.
b. like signs.
d. unequal magnitude.
2. When a glass rod is rubbed with silk and becomes positively charged,
a. electrons are removed from the rod.
c. protons are added to the silk.
b. protons are removed from the silk.
d. the silk remains neutral.
3. Charge is most easily transferred in
a. nonconductors.
c. semiconductors.
b. conductors.
d. insulators.
4. Which of the following is not true for both gravitational and electric forces?
a. The inverse square distance law applies.
b. Forces are proportional to physical properties.
c. Potential energy is a function of distance of separation.
d. Forces are either attractive or repulsive.
5. If the charge is tripled for two identical charges maintained at a constant separation, the electric force between
them will be changed by what factor?
a.
c. 9
b.
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d. 18
6. Electric field strength depends on
a. charge and distance.
c. Coulomb constant and mass.
b. charge and mass.
d. elementary charge and radius.
7. Coulomb's law says that the force between any two charges depends
a. directly on the size of the charges.
b. inversely on the square of the distance between the charges.
c. both A and B
d. none of the above
8. To say that electric charge is conserved means that no case has ever been found where
a. the total amount of charge on an object has increased.
b. one object has more charge than another object.
c. the total charge on an object has changed.
d. net charge has been created or destroyed.
e. none of the above
9. Charge carriers in a metal are electrons rather than protons, because electrons are
a. relatively far from a nucleus.
b. loosely bound.
c. lighter.
d. all of the above
e. none of the above
10. Two charged particles held close to each other are released. As the particles move, the velocity of each
increases. Therefore, the particles have
a. the same sign.
b. opposite signs.
c. charges that cannot be determined.
____ 11. Two charges separated a distance of 1.0 meter exert a 2.0-N force on each other. If the charges are pushed to a
separation of
a. 2.0 N.
b. 1.5 N.
c. 3.0 N.
d. 6.0 N.
e. 18.0 N.
meter, the force on each charge will be
Short Answer
12. Explain what happens when you vigorously rub your wool socks on a carpeted floor, touch a metal doorknob,
and get a shock.
13. Draw the lines of force representing the electric field surrounding two objects that have equal magnitude
charges of opposite polarity.
Problem
14. What is the electric force between a proton and an alpha particle (charge 2e) that are separated by a distance
of 3.0  10 m? (e = 1.60  10 C, k = 8.99  10 Nm /C )
Electrostatics practice test
Answer Section
MULTIPLE CHOICE
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
OBJ:
ANS:
OBJ:
ANS:
OBJ:
ANS:
OBJ:
ANS:
OBJ:
A
A
B
D
C
A
C
32.3
D
32.2
D
32.4
C
32.3
E
32.3
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
1
1
1
1
1
1
1
DIF:
DIF:
DIF:
DIF:
DIF:
DIF:
DIF:
PTS:
STA:
PTS:
STA:
PTS:
1
12.C
1
12.C
1
DIF: 2
REF: p. 504
DIF: 2
REF: p. 508
DIF: 3
REF: p. 504 | p. 505
DIF: 3
REF: p. 505
PTS: 1
I
I
I
I
II
I
2
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
REF:
16-1.1
16-1.1
16-1.2
16-2.2
16-2.2
16-3.1
p. 504
SHORT ANSWER
12. ANS:
Loosely held electrons are transferred from the carpet to the socks when the socks are rubbed against the
carpet. The body and socks have an excess of electrons and are negatively charged. Touching the doorknob
allows the electrons to escape. The shock felt is the sudden movement of charges as the body and socks return
to a neutral state.
PTS: 1
13. ANS:
PTS: 1
DIF: II
OBJ: 16-1.1
DIF: I
OBJ: 16-3.2
PROBLEM
14. ANS:
5.1  10
N
Given
q = +e =
C
q = +2e =
r=
C
m
N•m /C
Solution
PTS: 1
DIF: IIIA
OBJ: 16-2.1