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Physics 21 Practice Final Exam Review Questions Fall 2013
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1. A repelling force must occur between two charged objects under which conditions?
a. charges are of unlike signs
b. charges are of like signs
c. charges are of equal magnitude
d. charges are of unequal magnitude
B
2. A metallic object holds a charge of 3.8  106 C. What total number of electrons does this
represent? (e = 1.6  1019 C is the magnitude of the electronic charge.)
a. 4.2  1014
b. 6.1  1013
c. 2.4  1013
d. 1.6  1014
C
3. Two point charges, separated by 1.5 cm, have charge values of +2.0 and 4.0 µC, respectively.
What is the value of the mutual force between them? (ke = 8.99  109 Nm2/C2)
a. 320 N
b. 3.6  108 N
c. 8.0  1012 N
d. 3.1  103 N
A
4. Electric field is dimensionally equivalent to which of the following?
a. Nm/C
b. N/C
c. Nm2/C2
d. N/C2
B
5. In x-ray machines, electrons are subjected to electric fields as great as 6.0  105 N/C. Find an
electron’s acceleration in this field. (me = 9.11  1031 kg, e = 1.6  1019 C)
a. 1.1  1017 m/s2
b. 5.4  1013 m/s2
c. 4.6  1010 m/s2
d. 3.6  108 m/s2
A
6. A proton (+1.6  1019 C) moves 10 cm along the direction of an electric field of strength 3.0 N/C.
The electrical potential difference between the proton’s initial and ending points is:
a. 4.8  1019 V.
b. 0.30 V.
c. 0.033 V.
d. 30 V.
B
7. A 0.25-F capacitor is connected to a 400-V battery. Find the charge on the capacitor.
a. 1.2  1012 C
b. 1.0  104 C
c. 0.040 C
d. 0.020 C
B
8. Three capacitors of 1.0, 1.5, and 2.0 F are connected in series. Find the combined capacitance.
a. 4.5 F
b. 4.0 F
c. 2.2 F
d. 0.46 F
D
9. A 0.25-F capacitor is connected to a 400-V battery. What potential energy is stored in the
capacitor?
a. 1.2  1012 J
b. 1.0  104 J
c. 0.040 J
d. 0.020 J
D
10. A wire carries a steady current of 0.1 A over a period of 20 s. What total charge passes through
the wire in this time interval?
a. 200 C
b. 20 C
c. 2 C
d. 0.005 C
C
11. A light bulb has resistance of 240  when operating at 120 V. Find the current in the light bulb.
a. 2.0 A
b. 1.0 A
c. 0.50 A
d. 0.20 A
C
12. The quantity volt is equivalent to which of the following?
a. Jm
b. JC
c. C/
d. J/C
D
13. If a 500-W heater carries a current of 4.00 A, what is the resistance of the heating element?
a. 85.7 
b. 42.8 
c. 31.3 
d. 11.2 
C
14. Three resistors, with values of 2.0, 4.0 and 8.0 , respectively, are connected in series. What is
the overall resistance of this combination?
a. 0.58 
b. 1.1 
c. 7.0 
d. 14.0 
D
15. If R1 < R2 < R3, and if these resistors are connected in series in a circuit, which one dissipates the
greatest power?
a. R1
b. R2
c. R3
d. All are equal in power dissipation.
C
16. Three resistors, with values of 2.0, 4.0 and 8.0 , respectively, are connected in parallel. What is
the overall resistance of this combination?
a. 0.58 
b. 1.1 
c. 7.0 
d. 14.0 
B
17. Two resistors of values 6.0 and 12.0  are connected in parallel. This combination in turn is
hooked in series with a 2.0- resistor and a 24-V battery. What is the current in the 2-
resistor?
a. 2.0 A
b. 4.0 A
c. 6.0 A
d. 12 A
B
18. Assume that a uniform magnetic field is directed into this page. If an electron is released with an
initial velocity directed from the bottom edge to the top edge of the page, which of the following
describes the direction of the resultant force acting on the electron?
a. out of the page
b. to the right
c. to the left
d. into the page
B
19. A proton is released such that it has an initial speed of 4.0  105 m/s from left to right across the
page. A magnetic field of 1.2 T is present at an angle of 30 to the horizontal direction (or
positive x axis). What is the magnitude of the force experienced by the proton? (qp = 1.6  1019
C)
a. 4.8  1025 N
b. 1.3  1019 N
c. 3.8  1014 N
d. 7.5  103 N
C
20. The force exerted on a current-carrying wire located in an external magnetic field is directly
proportional to which of the following?
a. current strength
b. field strength
c. both a and b
d. None of the above are valid.
C
21. A wire is lying horizontally in the north-south direction and the horizontal magnetic field is
toward the east. Some positive charges in the wire move north and an equal number of negative
charges move south. The direction of the force on the wire will be:
a. east.
N
b. down, into the page.
c. up, out of the page.
W
E
d. There is no magnetic force.
S
B
22. A uniform 4.5-T magnetic field passes through the plane of a wire loop 0.10 m2 in area. What flux
passes through the loop when the direction of the 4.5-T field is at a 30 angle to the normal of the
loop plane?
a. 5.0 Tm2
b. 0.52 Tm2
c. 0.39 Tm2
d. 0.225 Tm2
C
23. The principle or law that says “an induced emf in a circuit loop produces a current whose
magnetic field opposes further change of magnetic flux” is credited to:
a. Faraday.
b. Lenz.
c. Ampere.
d. Volta.
B
24. A bar magnet is falling through a loop of wire with constant velocity. The south pole enters first.
As the magnet leaves the wire, the induced current (as viewed from above):
a. is clockwise.
b. is counterclockwise.
c. is zero.
d. is along the length of the magnet.
B
25. A straight wire of length  is oriented east-west and is in a magnetic field B pointing north. The wire
is moving downward at a constant speed v. Which end of the rod is positively charged?
a. neither
b. the east end
c. the west end
d. both ends
B
26. A ray of light strikes a thick sheet of glass (n = 1.5) at an angle of 25º with the normal. Find the
angle of the ray reflected off the glass surface with respect to the normal.
a. 56º
b. 46º
c. 39º
d. 25º
D
27. A ray of light strikes a thick sheet of glass (n = 1.5) at an angle of 25º with the normal. Find the
angle of the refracted ray within the glass with respect to the normal.
a. 56º
b. 46º
c. 25º
d. 16º
D
28. As a monochromatic light ray is transmitted through an air-to-glass boundary, what happens to
the wavelength?
a. increases
b. decreases
c. remains unchanged
d. approaches zero value
B
29. Which of the following describes what will happen to a light ray incident on a glass-to-air
boundary at greater than the critical angle?
a. total reflection
b. total transmission
c. partial reflection, partial transmission
d. partial reflection, total transmission
A
30. If a virtual image is formed along the principal axis 10 cm from a concave mirror with the focal
length 15 cm, what is the object distance from the mirror?
a. 30 cm
b. 10 cm
c. 12 cm
d. 6.0 cm
D
31. If a virtual image is formed 10.0 cm along the principal axis from a convex mirror of focal length
–15.0 cm, how far is the object from the mirror?
a. 30.0 cm
b. 10.0 cm
c. 6.00 cm
d. 3.00 cm
A
32. Which best describes the image of a concave mirror when the object is located somewhere
between the focal point and twice the focal point distance from the mirror?
a. virtual, upright and magnification greater than one
b. real, inverted and magnification less than one
c. virtual, upright and magnification less than one
d. real, inverted and magnification greater than one
D
33. Which of the following best describes the image of a concave mirror when the object is at a
distance greater than twice the focal point distance from the mirror?
a. virtual, upright and magnification greater than one
b. real, inverted and magnification less than one
c. virtual, upright and magnification less than one
d. real, inverted and magnification greater than one
B
34. If a wave from one slit of a double-slit set-up arrives at a point on the screen one wavelength behind
the wave from the other slit, what is observed at that point?
a. dark fringe
b. bright fringe
c. multi-colored fringe
d. gray fringe, neither dark nor bright
B
35. In a double-slit interference apparatus, by what factor is the distance between adjacent light and dark
fringes changed when the separation between slits is doubled?
a. 1/4
b. 1/2
c. 1
d. 2
B
36. A double-slit apparatus is set up so that a screen is positioned 1.6 m from the double slits and the
spacing between the two slits is 0.040 mm. What is the distance between alternating bright fringes on
the screen if the light source has a wavelength of 630 nm? (1 nm = 109 m)
a. 0.016 m
b. 0.025 m
c. 0.032 m
d. 0.047 m
B