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Physics 112
Exam I
Summer 2006
Name_________________
Physics 112
Summer 2006
Exam 1
Monday, Jun 26
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.
You have a sheet in the back of the test that you may use for any extra rough work.
When you are finished with the exam, place all exam materials, including the bubble
sheet, the exam itself, and scratch paper that you used for the exam, in your folder and
return the folder.
Good luck!
Page 1 of 9
Physics 112
Exam I
Summer 2006
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) F/9
B) F/3
C) 3F
D) 9F
E) Non 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) zero
B) 2.8 N
C) 4.0 N
D) 8.0 N
E) 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) 50 MN/C
B) 2.0 MN/C
C) 0.50 MN/C
D) 0.30 MN/C
E) 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 which
acts on any one of the charges?
A) 1.6 N
B) 1.8 N
C) 2.0 N
D) 2.2 N
E) 2.4 N
Page 2 of 9
Physics 112
Exam I
Summer 2006
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 from the sphere center of 1.0cm?
A) 0.9 x106 N/C
B) 9.0 x106 N/C
C) -0.9 x106 N/C
D) -9.0 x106 N/C
E) 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) 500 V
B) 50 V
C) 5.0 V
D) 0.50 V
E) 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) 1.3 × 106 m/s
B) 2.6 × 106 m/s
C) 1.3 × 107 m/s
D) 2.6 × 107 m/s
E) 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) 1200 N/C
B) 3000 N/C
C) 6000 N/C
D) 8000 N/C
E) 9000 N/C
Page 3 of 9
Physics 112
Exam I
Summer 2006
9. A parallel-plate capacitor consists of plates of area 1.5 × 10-4 m2 and separated by 1.0
mm. The capacitor is connected to a 12-V battery. What is the charge on the plates?
A) 1.6 × 10-11 C
B) 3.2 × 10-11 C
C) 1.6 × 10-14 C
D) 3.2 × 10-14 C
E) 1.6 × 10-19 C
10. Capacitances of 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) 10 μF
B) 15 μF
C) 25 μF
D) 60 μF
E) 66 μF
11. The length of a wire is doubled and the radius is doubled. By what factor does the
resistance change?
A) four times as large
B) twice as large
C) half as large
D) quarter as large
E) the same
12. Three resistors of 12, 12, 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) 1.0 A
B) 2.0 A
C) 3.0 A
D) 4.0 A
E) 6.0 A
Page 4 of 9
Physics 112
Exam I
Summer 2006
13. Three resistors of 12, 12, 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) 0.10 A
B) 0.20 A
C) 0.30 A
D) 0.40 A
E) 0.60 A
14. If the current flowing through a circuit of constant resistance is doubled, the power
dissipated by that circuit will
A) quadruple
B) double
C) decrease to one half
D) decrease to one fourth
E) 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) 4.2 V
B) 5.9 V
C) 120 V
D) 170 V
E) 240 V
16. You obtain a 100-W light bulb and a 50-W light bulb. Instead of connecting them in
the normal way, you devise a circuit that places them in series across normal household
voltage. Which statement is correct?
A) Both bulbs glow at the same reduced brightness
B) Both bulbs glow at the same increased brightness
C) Both bulbs glow at the same brightness as connected in parallel
D) The 100-W bulb glows brighter than the 50-W bulb
E) The 50-W bulb glows more brightly than the 100-W bulb
Page 5 of 9
Physics 112
Exam I
Summer 2006
17. An electric bulb with resistance of 48 Ω is connected to the battery with emf of 12 V
and internal resistance 2 Ω. Find current across the bulb.
A) 6.0 A
B) 4.0 A
C) 0.50 A
D) 0.25 A
E) 0.24 A
18. What 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 here is valid for the circuit shown?
A) 2 - I1 - 2I2 = 0
B) 2 - 2I1 - 2I2 - 4I3 = 0
C) 4 - I1 + 4I3 = 0
D) -2 - I1 - 2I2 = 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 be the voltage across the capacitor after 11 seconds?
A) 1.0 V
B) 3.0 V
C) 5.0 V
D) 7.0 V
E) 9.0 V
Page 6 of 9
Physics 112
Exam I
Summer 2006
Scratch Paper (intentionally left blank)
Page 7 of 9
Physics 112
Exam I
Summer 2006
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
11
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
10
20
Page 8 of 9
Physics 112
Exam I
Summer 2006
Answer Sheet
1
D) 9F
11
C) half as large
2
A) zero
12
B) 2.0 A
3
B) 2.0 MN/C
13
D) 0.40 A
4
A) 1.6 N
14
A) quadruple
5
E) 0
15
D) 170 V
6
C) 5.0 V
16
E) The 50-W bulb glows
more brightly than the
100-W bulb
17
E) 0.24 A
7
C) 1.3 × 107 m/s
8
C) 6000 N/C
18
D) The voltmeter should
be connected in series
with the resistance, to
measure potential across
the resistor.
(wrong statement)
9
A) 1.6 × 10-11 C
19
D) -2 - I1 - 2I2 = 0
10
B) 15 μF
20
B) 3 V
Page 9 of 9