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Physics 112
Exam I
Summer 2014
Name_________________
Physics 112
Summer 2014
Exam 1
Monday, Jun 30
Directions:
This 60-minute exam consists of twenty multiple-choice questions. This test is worth 20% of
your final grade. (One point is equal to 1% of the final grade.)
The questions on this test are not in order of difficulty.
You must mark all of your answers on both your test and answer sheet.
In marking the multiple choice bubble sheet use a number 2 pencil. Do not use ink. If you did
not bring a pencil, ask for one. Fill in the appropriate circles completely. If you need to change
any entry, you must completely erase your previous entry.
Carefully read each question and its five possible answers. Select one and only one answer for
each question. Choose the answer that is closest to the correct one.
When you are finished with the exam, return the bubble sheet, the exam itself, and scratch paper
that you used for the exam.
Good luck!
Page 1 of 7
Physics 112
Exam I
Summer 2014
1. Two charges are separated by a distance d and exert mutual attractive forces of F on each
other. If the charges are separated by a distance of d/3, what are the new mutual forces?
A)
B)
C)
D)
E)
F/9
F/3
3F
9F
None of these
2. A point charge of +Q is placed at the center of a square. When a second point charge of -Q
is placed at one of the square's corners, it is observed that an electrostatic force of 2.0 N acts
on the positive charge at the square's center. Now, identical charges of -Q are placed at the
other three corners of the square. What is the magnitude of the net electrostatic force acting
on the positive charge at the center of the square?
A)
B)
C)
D)
E)
Zero
2.8 N
4.0 N
8.0 N
16N
3. A force of 10 N acts on a charge of 5.0 μC when it is placed in a uniform electric field. What
is the magnitude of this electric field?
A)
B)
C)
D)
E)
50 MN/C
2.0 MN/C
0.50 MN/C
0.30 MN/C
0.10 MN/C
4. Three identical charges of 3.0 μC are placed at the vertices of an equilateral triangle which
measures 30 cm on a side. What is the magnitude of the electrostatic force that acts on any
one of the charges?
A)
B)
C)
D)
E)
1.6 N
1.8 N
2.0 N
2.2 N
2.4 N
Page 2 of 7
Physics 112
Exam I
Summer 2014
5. A solid metal sphere of radius 2.0 cm carries a total charge of -0.1 μC. What is the
magnitude of the electric field at a distance of 1.0cm from the sphere’s center?
A)
B)
C)
D)
E)
0.9 x106 N/C
9.0 x106 N/C
-0.9 x106 N/C
-9.0 x106 N/C
0
6. It takes 50 J of energy to move 10 C of charge from point A to point B. What is the potential
difference between points A and B?
A)
B)
C)
D)
E)
500 V
50 V
5.0 V
0.50 V
0.050 V
7. A stationary electron is accelerated through a potential difference of 500 V. What is the
velocity of the electron afterward?
A)
B)
C)
D)
E)
1.3 × 106 m/s
2.6 × 106 m/s
1.3 × 107 m/s
2.6 × 107 m/s
1.3 × 108 m/s
8. A parallel-plate capacitor has plates of area 0.20 m2 separated by a distance of 1.0 mm.
What is the strength of the electric field between these plates when this capacitor is
connected to a 6.0-V battery?
A)
B)
C)
D)
E)
1200 N/C
3000 N/C
6000 N/C
8000 N/C
9000 N/C
Page 3 of 7
Physics 112
Exam I
Summer 2014
9. A parallel-plate capacitor consists of plates of area 1.5 × 10-4 m2, which are separated by 1.0
mm. The capacitor is connected to a 12-V battery. What is the charge on the plates?
A)
B)
C)
D)
E)
1.6 × 10-11 C
3.2 × 10-11 C
1.6 × 10-14 C
3.2 × 10-14 C
1.6 × 10-19 C
10. Two capacitors, 10 μF and 20 μF, are connected in parallel, and this pair is then connected in
series with a 30-μF capacitor. What is the equivalent capacitance of this arrangement?
A)
B)
C)
D)
E)
10 μF
15 μF
25 μF
60 μF
66 μF
11. The length of a wire is doubled and the radius is doubled. By what factor does the resistance
change?
A)
B)
C)
D)
E)
Increase by 4 times
Increase by 2 times
Decrease by 2 times
Decrease by 4 times
Remains the same
12. Three resistors of 12 Ω, 12 Ω, and 6.0 Ω are connected in parallel. A 12-V battery is
connected to the combination. What is the current through the 6.0-Ω resistor?
A)
B)
C)
D)
E)
1.0 A
2.0 A
3.0 A
4.0 A
6.0 A
Page 4 of 7
Physics 112
Exam I
Summer 2014
13. Three resistors of 12 Ω, 12 Ω, and 6.0 Ω are connected in series. A 12-V battery is
connected to the combination. What is the current through the battery?
A)
B)
C)
D)
E)
0.10 A
0.20 A
0.30 A
0.40 A
0.60 A
14. If the current flowing through a circuit of constant resistance is doubled, the power dissipated
by that circuit will
A)
B)
C)
D)
E)
quadruple
double
decrease by one-half
decrease by one-fourth
remain the same
15. A 500-W device is connected to a 120-V ac power source. What is the peak voltage across
this device?
A)
B)
C)
D)
E)
4.2 V
5.9 V
120 V
170 V
240 V
16. You obtain a 100-W light bulb and a 50-W light bulb. Instead of connecting them in the
normal way (in parallel), you devise a circuit that places them in series across a normal
household voltage. Which statement is correct?
A)
B)
C)
D)
E)
Both bulbs glow at the same reduced brightness
Both bulbs glow at the same increased brightness
Both bulbs glow at the same brightness as connected in parallel
The 100-W bulb glows brighter than the 50-W bulb
The 50-W bulb glows brighter than the 100-W bulb
Page 5 of 7
Physics 112
Exam I
Summer 2014
17. An electric bulb with resistance of 48 Ω is connected to the battery with emf of 12 V and
internal resistance of 2 Ω. Find current across the bulb.
A)
B)
C)
D)
E)
6.0 A
4.0 A
0.50 A
0.25 A
0.24 A
18. Which statement is wrong?
A) At any junction point in an electric circuit, the sum of all currents entering the junction must
equal to the sum of all currents leaving the junction.
B) The sum of the changes in potential around any closed path of a circuit must be zero.
C) The ammeter should be inserted in series with the resistance, to measure the current in this
resistance.
D) The voltmeter should be connected in series with the resistance, to measure potential across
the resistor.
E) Resistance of an ideal ammeter is zero.
19. Which of the equations below is valid for the circuit shown? (Current I is in amperes)
A) 2 - I1 - 2I2 = 0
B) 2 - 2I2 - 4I3 = 0
C) 4 - I1 + 4I3 = 0
D) 2 - I1 - 2I3 = 0
E) 6 - I1 - 2I2 = 0
20. A 2.0-μF capacitor is charged to 12 V and then discharged through a 4.0 × 106 Ω resistor.
What will the voltage across the capacitor be after 11 seconds?
A)
B)
C)
D)
E)
1.0 V
3.0 V
5.0 V
7.0 V
9.0 V
Page 6 of 7
Physics 112
Exam I
Summer 2014
Record Sheet
You may fill in this sheet with your choices, detach it and take it with you after the exam for
comparison with the posted answers
1
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2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
10
20
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