Download Physics 202 Midterm 1 Practice Exam

Physics 202 Midterm 1
Practice Exam
Name: ___________________________________ Student ID: ______________
Section: ___________________________________
TA (please circle):
Daniel Crow
Aaron Levine
Scott Douglas
Andrew Loveridge
Yutao Gong
Jason Milhone
Taylor Klaus
Hojin Yoo
Instructions:
1. Don't forget to write down your name, student ID#, and section number. You need to do this on
(this page of your test book and on your Scantron sheet as well, where you should fill in your
student ID number under Identification number and your three digit section number starting with 3
under special codes).
2. Answer all multiple questions in this test book by indicating the best answer among choices.
You must do this both on your test book and on your Scantron sheet. Follow instructions on the
Scantron sheet on how to mark valid answers.
3. When you finish, you need to turn in both this test book and the Scantron sheet.
4. Use the blank side of question pages as additional draft spaces. An extra bank sheet is provided
at the end of the test book.
5. Only one answer is allowed per problem/question/ All problems have equal weight.
Constants: ke = 8.99 x 109 Nm2 /C2
1. Two small spheres attract one another electrostatically. This can occur for a variety of
reasons. Which of the following statements must be true?
A) at least one sphere is charged
B) neither is charged
C) both are charged
D) both have the same charge
E) None of these is correct.
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2. Three charges +q, +Q, and –Q are placed at the corners of an equilateral triangle as shown.
The net force on charge +q due to the other two charges is
A)
B)
C)
D)
E)
vertically up.
vertically down.
zero.
horizontal to the left.
horizontal to the right.
3. Two charges Q1 and Q2 are distance d apart. If the electric field is zero at distance 3d/2
from Q1 and d/2 from Q2 , along the line joining Q1 and Q2 , then what is the relation
between Q1 and Q2 ?
A) Q1 = 9Q2
B) Q1 = –Q2 /9
C) Q1 = Q2 /3
D) Q1 = –3Q2
E) Q1 = –9Q2
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4. In the diagram, Q1 = 9.0 µC and Q2 = –9.0 µC. If Q2 has a mass of 3.0 g, a uniform electric
field of 1.8 kN/C imposed in the positive y direction would give this particle an acceleration
in the y direction of approximately
A)
B)
C)
D)
E)
zero
5.4 m/s2
6.8 cm/s2
4.5 m/s2
7.5 cm/s2
5. An electron is released from rest in a uniform electric field. If the electric field is 1.25 kN/C,
at the end of 20 ns the electron's velocity will be approximately
A) 2.5 × 10– 5 m/s
B) 3.9 × 103 m/s
C) 3.0 × 108 m/s
D) 2.5 × 103 m/s
E) 4.4 × 106 m/s
6. A uniform circular ring has charge Q and radius r. The magnitude of the electric field at a
distance of r along the axis of the ring is Eo . If the radius were to double, then calculate the
new electric field at a distance of r along the axis of the ring in terms of Eo .
A) 0.40 Eo
B) 0.25 Eo
C) 0.50 Eo
D) 0.20 Eo
E) 0.089 Eo
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7. The figure shows a surface enclosing the charges 2q and –q. The net flux through the
surface surrounding the two charges is
A) q/∈0
B) 2q/∈0
C) –q/∈0
D) zero
E) None of these is correct.
8. An infinitely long cylindrical shell of radius 6.0 cm carries a uniform surface charge density
σ = 12 nC/m2 . The electric field at r = 10.0 cm is approximately
A) 12 kN/C
B) 0.56 kN/C
C) 1.3 kN/C
D) 0.81 kN/C
E) zero
9. A solid sphere of radius a is concentric with a hollow sphere of radius b, where b > a. If the
solid sphere has a charge +Q and the hollow sphere a charge of –Q, the electric field at
radius r, where a < r < b, is which of the following, in terms of k = (4π∈0 )– 1?
A)
B)
C)
D)
E)
kQ/r2
2kQ/r2
kQ/a2
kQ/b2
kQ/(b – a)2
Page 4
10. A solid spherical conductor has a radius of 15 cm. The electric field 30.0 cm from the center
of this sphere has a magnitude of 800.0 N/C. What is the surface charge density σ on the
sphere?
A) 7.1 × 10– 9 C/m2
B) 1.0 × 10– 8 C/m2
C) 1.4 × 10– 8 C/m2
D) 2.8 × 10– 8 C/m2
E) 1.1 × 10– 7 C/m2
11. A charge of 2.0 mC is located in a uniform electric field of intensity 4.0 × 105 N/C. How
much work is required to move this charge 20.0 cm along a path making an angle of 60.0°
with the electric field?
A) 0.14 J
B) 0.34 J
C) 80 mJ
D) 14 J
E) 8.0 J
12. Two charges Q1 (= +6 µC) and Q2 (= –2 µC) are brought from infinity to positions on the
x-axis of x = –4 cm and x = +4 cm, respectively. How much work approximately was done
in bringing the charges together? (Round your answer to 1 significant figure)
A) –2 × 106 J
B) –9 × 105 J
C) –20 J
D) –1 J
E) none of the above
Page 5
13. A charge of 100 nC resides on the surface of a spherical shell of radius 20 cm. The electric
potential at a distance of 50 cm from the center of the spherical shell is approximately
A)
B)
C)
D)
E)
20 V
200 V
2000 V
20,000 V
None of these is correct.
14. The figure shows portions of four equipotential surfaces whose potentials are related as
follows: V1 > V2 > V3 > V4 . The lines represent four paths (A → A', B→ B', C → C', D
→ D') along which equal test charges are moved. The work involved can be said to be
A)
B)
C)
D)
E)
the greatest for path A → A'.
the greatest for path B → B'.
the greatest for path C → C'.
the greatest for path D → D'.
the same for all paths.
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Use the following to answer question 15.
15. The electrostatic potential energy of the system of point charges q1 = 1.00 µC, q2 = 2.00
µC, and q3 = 3.00 µC at the corners of the equilateral triangle whose side s = 30.0 cm is
A) 1.10 J
B) 0.990 J
C) 0.631 J
D) 0.330 J
E) 0.123 J
16. An 80-nF capacitor is charged to a potential of 500 V. How much charge accumulates on
each plate of the capacitor?
A) 4 × 10– 4 C
B) 4 × 10– 5 C
C) 4 × 10–10 C
D) 2 × 10–10 C
E) 2 × 10– 7 C
17. If you increase the charge on a parallel-plate capacitor from 3 µC to 9 µC and increase the
plate separation from 1 mm to 3 mm, the energy stored in the capacitor changes by a factor
of
A) 27
B) 9
C) 3
D) 8
E) 1/3
Page 7
18. If C1 < C2 < C3 < C4 for the combination of capacitors shown, the equivalent capacitance
A)
B)
C)
D)
E)
is less than C1 .
is more than C4 .
is between C2 and C3 .
is less than C2 .
could be any value depending on the applied voltage.
19. A charged capacitor has an initial electric field
and potential difference V0 across its
plates. Without connecting any source of emf, you insert a dielectric (κ > 1) slab between
the plates to produce an electric field
and a potential difference Vd across the capacitor.
The pair of statements that best represents the relationships between the electric fields and
potential differences is
A)
>
; Vd > V0
B)
=
; Vd > V0
C)
>
; Vd = V0
D)
<
; Vd > V0
E)
<
; Vd < V0
20. The capacitance of a parallel-plate capacitor is 24 µF when the plates are separated by a
material of dielectric constant 2.0. If this material is removed, leaving air between the
plates, and the separation between the plates is tripled, the capacitance is
A) unchanged
B) 16 µF
C) 36 µF
D) 0.14 mF
E) 4.0 µF
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Answer Key - Midterm1_practice
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A
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E
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B
A
B
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E
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