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Physics 112
Exam I
Spring 2006
Name_________________
Physics 112
Spring 2006
Exam 1
Wednesday, Feb 8
Directions:
This 50-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 the 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.
Be sure to write you name on every sheet.
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
Spring 2006
1. A downward force is exerted on a negative charge. What is the direction of the
electric field at the point where the charge is located?
A.
B.
C.
D.
E.
Left
Right
Upward
Downward
Not enough information to answer the question
2. Two particles of equal charge, Q = 1.0 μC are located at the corners of an equilateral
triangle of side d = 10.0 cm. What is the magnitude of the electric field at the third
corner of the triangle?
A.
B.
C.
D.
E.
0.9 x106 N/C
1.6 x106 N/C
3.2 x106 N/C
4.8 x106 N/C
0
3. Four particles of equal charge, Q = 1.0 μC are located at the corners of a square of
side d = 10.0 cm. What is the electric field at the center of the square?
A.
B.
C.
D.
E.
0.9 x106 N/C
1.6 x106 N/C
3.2 x106 N/C
4.8 x106 N/C
0
4. The electric field lines in a certain region of space are as shown below. Compare the
magnitude of the electric field at points 1, 2 and 3.
1
A.
B.
C.
D.
E.
2
3
E1 = E2 = E3
E1 = E2 > E3
E1 > E2 > E3
E1 = E2 < E3
E1 = E2; E3=0
Page 2 of 9
Physics 112
Exam I
Spring 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.
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. An unknown electric charge is placed in the center of a cubic box. What will happen
with the flux from the box if each side of the box will be doubled, but the charge will
remain unchanged?
A.
B.
C.
D.
E.
The flax will remain the same
The flax will be doubled
The flax will increase four times
The flax will decrease two times
The flax will decrease four times
7. An electron (charge q = 1.60x10-19 C, and mass m = 9.11x10-31 kg) is accelerated in a
uniform field between two parallel charged plates. Potential difference between the
plates is V = 1000 V. The electron is accelerated from rest near the negative plate.
What is the speed of the electron as it reaches the positive plate?
A.
B.
C.
D.
E.
1.2 x107
1.9 x107
2.5 x107
3.2 x107
4.1 x107
m/s
m/s
m/s
m/s
m/s
8. Five identical capacitors, 50 μF each, are connected in series, and are then connected
to a battery of 3 V. What charge is stored in each capacitor?
A.
B.
C.
D.
E.
30 μC
60 μC
83 μC
150 μC
750 μC
Page 3 of 9
Physics 112
Exam I
Spring 2006
9. How does the energy stored in the capacitor change if the potential difference
between the plates of the capacitor is doubled?
A.
B.
C.
D.
E.
Increased twice
Decreased twice
Increased four times
Decreased four times
Remains the same
10. Ten resistors 50  each are connected in parallel. What is the effective resistance?
A.
B.
C.
D.
E.
5
10 
50 
100 
500 
11. Two cylindrical resistors, R1 and R2, are made of identical material. R2 has twice the
length of R1 but half the radius of R1. They are connected to a battery as shown. The
internal resistance of the battery can be neglected. The ratio of currents I1 /I2 flowing
through R1 and R2 is equal to
I1
A.
B.
C.
D.
E.
I2
0.5
1
2
4
8
Page 4 of 9
Physics 112
Exam I
Spring 2006
12. Two resistors R1 = 5  and R2 = 10  are connected in series and are then connected
to a battery with emf, ε = 12 V. The internal resistance of the battery can be
neglected. Find the electric power delivered by the battery.
A.
B.
C.
D.
E.
1.6 W
3.2 W
6.4 W
9.6 W
12.8 W
13. A battery with emf of 12 V and internal resistance 2 Ω is connected to the resistance
of 22 Ω. What is the terminal voltage of the battery?
A. 12 V
B. 11 V
C. 10 V
D. 9 V
E. 3 V
14. What is the resistance of an electric light bulb that consumes 100 W when connected
to a 120 V outlet?
A.
B.
C.
D.
E.
1.2 Ω
100 Ω
120 Ω
144 Ω
12 k Ω
15. What is the peak (amplitude) value of voltage in the standard 120 V line used in US?
A.
B.
C.
D.
E.
110 V
120 V
170 V
240 V
360 V
Page 5 of 9
Physics 112
Exam I
Spring 2006
16. Two batteries with ε1 = 9.0 V and ε2 = 6.0 V, and two resistors R1 = 30 Ω and R2 =
30 Ω are connected as shown below. What is the current in resistance R1?
1
R1
R2
2
A.
B.
C.
D.
E.
0
0.1 A
0.2 A
0.3 A
0.5 A
17. 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.
18. The relaxation time of the RC circuit is 10.0 s. The initial current (during the
discharging process) is 10.0 mA. What current will be after 20.0 s?
A.
B.
C.
D.
E.
0
1.35 mA
3.68 mA
5.00 mA
10.0 mA
Page 6 of 9
Physics 112
Exam I
Spring 2006


19. Positive charge q is moving with velocity v in the magnetic field B as shown below


(with vectors v and B on the surface of the page). What is the direction of the
magnetic force?

v
q
A.
B.
C.
D.
E.


B

Parallel to v

Parallel to B


Exactly between v and B
Into the page
Out of the page
20. A positively charged particle is moving in a magnetic field. What is the angle
between the velocity of the charge and the direction of the magnetic field if the
magnetic force on the particle is zero?
A.
B.
C.
D.
E.
90°
45°
30°
0
Magnetic force can not be zero if the speed of the particle and the magnetic field
are not zero.
Page 7 of 9
Physics 112
Exam I
Spring 2006
Scratch Paper (intentionally left blank)
Page 8 of 9
Physics 112
Exam I
Spring 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 9 of 9