Name: ________________________ Class: ___________________ Date: __________
PHYS 102--Exam 1--Spring 2015
Multiple Choice
Identify the choice that best completes the statement or answers the question.
4. In this figure, a -Q charge sits in the middle of a
square that has 4 charges at each corner. The net
force vector on the -Q charge lies in which of the
quadrants?
1. A metallic object holds a charge of −3.8 × 10−6 C.
What total number of electrons does this represent?
a. 2.4 × 1013
b. 1.6 × 1014
c. 6.1 × 1013
d. 4.2 × 1014
2. What happens when you bring a negatively charged
plastic rod near to but do not touch the end of a
neutral copper wire that is able to rotate about its
center (as in this figure)?
a.
b.
c.
d.
a.
b.
c.
d.
e.
The wire will be attracted to the plastic rod
The wire will move away from the rod
Nothing will happen unless the two objects
touch
It depends on the length of the wire.
5. If the distance between 2 negatively charged ions is
doubled, the force on one of them due to the other
wil:
a. increase by a factor of 2
b. remain the same
c. decrease by a factor of 2
d. decrease by a factor of 4
e. increase by a factor of 4
3. Two charged balls are repelling each other as they
hang from the ceiling. What can you say about
their charges?
a.
b.
c.
d.
I
II
III
IV
there is no net force
one is positive, one is negative
both are positive
both are negative
either both are positive or both are negative
1
9. This diagram shows two charges and their electric
field lines. At what point is the magnitude of the
electric field the largest?
6. The diagram shows three heavily charged plastic
cubes. The net force on cube #3 is shown. If cube
#3 is positively charged, what are the charges on
cubes 1 and 2, respectively?
a.
b.
c.
d.
e.
cube 1 is positive; cube 2 is negative
cube 1 is positive; cube 2 is positive
cube 1 is negative; cube 2 is positive
cube 1 is positive; cube 2 is negative
cube 1 and cube 2 are both positive
a.
b.
c.
d.
e.
7. Consider these two charges and their resultant
electric field lines. If q 2 has a charge of +2 C, what
is the charge on q1?
A
B
C
D
the E-field is the same at all points
10. You are sitting a certain distance from a point
charge, and you measure an electric field of E o. If
your distance from the charge is halved, what is the
new electric field that you measure?
a. Eo
b. Eo/4
c. Eo/8
d. 4 Eo
e. 8 Eo
a.
b.
c.
d.
11. Who is Dr. Young’s favorite student?
a. Jeff Thibodeaux
b. Jessica Gauthreaux
c. Riley Griffin
d. Taylor Hebert
e. Me!
+2 C
-16 C
+8 C
+16 C
8. Which of these is not a unit for the electric field?
N
a.
C
V
b.
m
kg m
c.
s2 C
d. all of these are units for the electric field
2
12. Consider this collection of charges and the
Gaussian surface. Which of these best describe the
total flux through the surface?
a.
b.
c.
d.
13. This figure shows the gravitational field
represented with the arrows. This field has a
magnitude of 10 m/s2. The Gaussian surface is the
thick vertical line; this surface has an area of 2 m 2.
The field and surface are situated at an angle θ.
Which of these best describes the flux, φ, through
the surface?
φ<0
φ=0
φ>0
a.
it is impossible to tell
b.
c.
d.
3
φ<20
φ>20
φ=20
none of these
Problem
14. What is the gravitational potential energy contained in this collection of masses?
.
4
15. In 1 or 2 sentences, describe Newton’s shell
theorem.
17. A 3 C charge is accelerated by a constant electric
field of magnitude 60 N/C; the mass of the charge
is 2 kg. (a) Find the acceleration of the particle. (b)
What is the particle's displacement after 2 s,
assuming it starts from rest.
16. What is the acceleration due to gravity at a distance
of 100,000 meters above the surface of the Earth?
5
18. For this figure, what is the magnitude and direction of the electric field at point A?
19. (10 pts) Consider this dipole. Label the electric field and equipotential lines. Draw, at least, 6 electric field and 6
equipotential lines.
6
E = (2.0)i + (3.0y)j
20. Consider this cube, which is 3m on each side. The electric field measured around the cube is ä
N/C.
a) What is the net flux, φ, through this cube?
b) What is the total charge enclosed within the cube?
7
ID: A
PHYS 102--Exam 1--Spring 2015
Answer Section
MULTIPLE CHOICE
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
A
A
D
B
D
C
C
D
B
D
E
C
A
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
1
1
1
1
1
1
1
1
1
1
1
1
1
REF:
REF:
REF:
REF:
REF:
REF:
REF:
REF:
REF:
REF:
S15
S15
S15
S15
S15
S15
S15
S15
S15
S15
PROBLEM
14. ANS:
.
PTS: 1
15. ANS:
.
PTS: 1
16. ANS:
.
PTS: 1
17. ANS:
.
PTS: 1
18. ANS:
10.4 N/C
PTS: 1
19. ANS:
.
PTS: 1
1
ID: A
20. ANS:
.
PTS: 1
2