Chapter 21: The Electric Field I: Discrete Charge Distributions

1
Chapter 21 The Electric Field I Discrete
Charge Distributions

• Section 21-1 Charge

2
Electric charges of the same sign

1. attract each other.
2. repel each other.
3. exert no forces on each other.

3
Electric charges of the same sign

1. attract each other.
2. repel each other.
3. exert no forces on each other.

4
Electric charges of the opposite sign

1. attract each other.
2. exert no forces on each other.
3. repel each other.

5
Electric charges of the opposite sign

1. attract each other.
2. exert no forces on each other.
3. repel each other.

6
Electrons

1. are about 2000 times more massive than protons.
2. are about 2000 times less massive than protons.
3. have about 2000 times more charge than protons.
4. have about 2000 times less charge than protons.
5. can have any amount of charge.

7
Electrons

1. are about 2000 times more massive than protons.
2. are about 2000 times less massive than protons.
3. have about 2000 times more charge than protons.
4. have about 2000 times less charge than protons.
5. can have any amount of charge.

8
Protons

1. are about 2000 times more massive than electrons.
   
2. are about 2000 times less massive than electrons.
   
3. have about 2000 times more charge than electrons.
   
4. have about 2000 times less charge than electrons.
   
5. can have any amount of charge.

9
Protons

1. are about 2000 times more massive than electrons.
   
2. are about 2000 times less massive than electrons.
   
3. have about 2000 times more charge than electrons.
   
4. have about 2000 times less charge than electrons.
   
5. can have any amount of charge.

10
Experimental evidence indicates that

1. charge is quantized and conserved.
2. charge is quantized but not conserved.
3. charge is conserved but not quantized.
4. charge is neither quantized nor conserved.

11
Experimental evidence indicates that

1. charge is quantized and conserved.
2. charge is quantized but not conserved.
3. charge is conserved but not quantized.
4. charge is neither quantized nor conserved.

12
An electron (q ?e) and a positron (q ?e) can
combine to give off two gamma rays. The net
change in the algebraic sum of the charges before
and after the combination is

1. 2e
2. zero
3. ?2e
4. e
5. ?e

13
An electron (q ?e) and a positron (q ?e) can
combine to give off two gamma rays. The net
change in the algebraic sum of the charges before
and after the combination is

1. 2e
2. zero
3. ?2e
4. e
5. ?e

14
How many electrons must be transferred to a body
to produce a charge of 125 nC?

1. 1.25 107
2. 1.60 1019
3. 1.28 1012
4. 3.45 1011
5. 7.81 1011

15
How many electrons must be transferred to a body
to produce a charge of 125 nC?

1. 1.25 107
2. 1.60 1019
3. 1.28 1012
4. 3.45 1011
5. 7.81 1011

16
A particular nucleus of the element erbium
contains 68 protons and 90 neutrons. What is the
total number of electrons in the neutral erbium
atom?

1. 90
2. 158
3. 22
4. 68
5. None of the above

17
A particular nucleus of the element erbium
contains 68 protons and 90 neutrons. What is the
total number of electrons in the neutral erbium
atom?

1. 90
2. 158
3. 22
4. 68
5. None of the above

18
Chapter 21 The Electric Field I Discrete
Charge Distributions

• Section 21-2 Conductors and Insulators and
  Concept Check 21-1a, 21-1b and 21-2

19
Two identical conducting spheres, one that has an
initial charge Q, the other initially uncharged,
are brought into contact. What is the new charge
on each sphere?

1. -Q
2. -Q/2
3. zero
4. Q/2
5. Q

20
Two identical conducting spheres, one that has an
initial charge Q, the other initially uncharged,
are brought into contact. What is the new charge
on each sphere?

1. -Q
2. -Q/2
3. zero
4. Q/2
5. Q

21
Two identical conducting spheres, one that has an
initial charge Q, the other initially uncharged,
are brought into contact. While the spheres are
in contact, a positively charged rod is moved
close to one sphere, causing a redistribution of
the charges on the two spheres so the charge on
the sphere closest to the rod has a charge of -Q.
What is the charge on the other sphere?

1. -2Q
2. -Q
3. zero
4. Q
5. 2Q

22
Two identical conducting spheres, one that has an
initial charge Q, the other initially uncharged,
are brought into contact. While the spheres are
in contact, a positively charged rod is moved
close to one sphere, causing a redistribution of
the charges on the two spheres so the charge on
the sphere closest to the rod has a charge of -Q.
What is the charge on the other sphere?

1. -2Q
2. -Q
3. zero
4. Q
5. 2Q

23
Two identical conducting spheres are charged by
induction and then separated by a large distance
sphere 1 has charge Q and sphere 2 has charge
-Q. A third identical sphere is initially
uncharged. If sphere 3 is touched to sphere 1 and
separated, then touched to sphere 2 and
separated, what is the final charge on each of
the three spheres?

1. Q1 Q/4, Q2 Q/4, Q3 -Q/2
2. Q1 -Q/2, Q2 Q/4, Q3 Q/4
3. Q1 Q/2, Q2 -Q/4, Q3 -Q/4
4. Q1 -Q/4, Q2 -Q/2, Q3 -Q/2
5. Q1 -Q/2, Q2 Q/2, Q3 Q/2

24
Two identical conducting spheres are charged by
induction and then separated by a large distance
sphere 1 has charge Q and sphere 2 has charge
-Q. A third identical sphere is initially
uncharged. If sphere 3 is touched to sphere 1 and
separated, then touched to sphere 2 and
separated, what is the final charge on each of
the three spheres?

1. Q1 Q/4, Q2 Q/4, Q3 -Q/2
2. Q1 -Q/2, Q2 Q/4, Q3 Q/4
3. Q1 Q/2, Q2 -Q/4, Q3 -Q/4
4. Q1 -Q/4, Q2 -Q/2, Q3 -Q/2
5. Q1 -Q/2, Q2 Q/2, Q3 Q/2

25
Two small spheres attract one another
electrostatically. This can occur for a variety
of reasons. Which of the following statements is
true?

1. At least one sphere must be charged.
2. Neither sphere need be charged.
3. Both spheres must be charged and the charges must
   have the same sign.
4. Both spheres must be charged and the charges must
   have opposite signs.

26
Two small spheres attract one another
electrostatically. This can occur for a variety
of reasons. Which of the following statements is
true?

1. At least one sphere must be charged.
2. Neither sphere need be charged.
3. Both spheres must be charged and the charges must
   have the same sign.
4. Both spheres must be charged and the charges must
   have opposite signs.

27
Two small spheres repel one another
electrostatically. Which of the following
statements is true?

1. At least one sphere must be charged.
2. Neither sphere need be charged.
3. Both spheres must be charged and the charges must
   have the same sign.
4. Both spheres must be charged and the charges must
   have opposite signs.

28
Two small spheres repel one another
electrostatically. Which of the following
statements is true?

1. At least one sphere must be charged.
2. Neither sphere need be charged.
3. Both spheres must be charged and the charges must
   have the same sign.
4. Both spheres must be charged and the charges must
   have opposite signs.

29
If you bring a positively charged insulator near
two uncharged metallic spheres that are in
contact and then separate the spheres, the sphere
on the right will have

1. no net charge.
2. a positive charge.
3. a negative charge.

30
If you bring a positively charged insulator near
two uncharged metallic spheres that are in
contact and then separate the spheres, the sphere
on the right will have

1. no net charge.
2. a positive charge.
3. a negative charge.

31
If you bring a negatively charged insulator near
two uncharged metallic spheres that are in
contact and then separate the spheres, the sphere
on the right will have

1. no net charge.
2. a positive charge.
3. a negative charge.

32
If you bring a negatively charged insulator near
two uncharged metallic spheres that are in
contact and then separate the spheres, the sphere
on the right will have

1. no net charge.
2. a positive charge.
3. a negative charge.

33
A uniformly positively charged spherical
conductor is placed midway between two identical
uncharged conducting spheres. How would the
charges in the middle sphere be distributed?

1. The positive charges stay uniformly distributed
   on the surface of the middle sphere.
2. There are more positive charges near the top and
   bottom of the sphere compared to the sides next
   to the two other spheres.
3. There are more positive charges near the sides of
   the spheres that are next to the other two
   spheres compared to the other regions of the
   sphere.
4. There are more positive charges near the front
   and back of the sphere compared to the sides next
   to the two other spheres.
5. None of these is correct.

34
A uniformly positively charged spherical
conductor is placed midway between two identical
uncharged conducting spheres. How would the
charges in the middle sphere be distributed?

1. The positive charges stay uniformly distributed
   on the surface of the middle sphere.
2. There are more positive charges near the top and
   bottom of the sphere compared to the sides next
   to the two other spheres.
3. There are more positive charges near the sides of
   the spheres that are next to the other two
   spheres compared to the other regions of the
   sphere.
4. There are more positive charges near the front
   and back of the sphere compared to the sides next
   to the two other spheres.
5. None of these is correct.

35
Chapter 21 The Electric Field I Discrete
Charge Distributions

• Section 21-3 Coulombs Law

36
Two small spheres, each with mass m 5.0 g and
charge q, are suspended from a point by threads
of length L 0.30 m. What is the charge on each
sphere if the threads make an angle theta of 20º
with respect to the vertical?

1. 7.9 107 C
2. 2.9 107 C
3. 7.5 102 C
4. 6.3 1013 C
5. 1.8 107 C

37
Two small spheres, each with mass m 5.0 g and
charge q, are suspended from a point by threads
of length L 0.30 m. What is the charge on each
sphere if the threads make an angle theta of 20º
with respect to the vertical?

1. 7.9 107 C
2. 2.9 107 C
3. 7.5 102 C
4. 6.3 1013 C
5. 1.8 107 C

38
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

1. up.
2. down.
3. along a diagonal.
4. to the left.
5. to the right.

39
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

1. up.
2. down.
3. along a diagonal.
4. to the left.
5. to the right.

40
Charges q1 and q2 exert repulsive forces of 10 N
on each other. What is the repulsive force when
their separation is decreased so that their final
separation is 80 of their initial separation?

1. 16 N
2. 12 N
3. 10 N
4. 8.0 N
5. 6.4 N

41
Charges q1 and q2 exert repulsive forces of 10 N
on each other. What is the repulsive force when
their separation is decreased so that their final
separation is 80 of their initial separation?

1. 16 N
2. 12 N
3. 10 N
4. 8.0 N
5. 6.4 N

42
A proton is about 2000 times more massive that an
electron but they both have charges of the same
magnitude. The magnitude of the force on an
electron by a proton is ____ the magnitude of the
force on the proton by the electron.

1. greater than
2. equal to
3. less than

43
A proton is about 2000 times more massive that an
electron but they both have charges of the same
magnitude. The magnitude of the force on an
electron by a proton is ____ the magnitude of the
force on the proton by the electron.

1. greater than
2. equal to
3. less than

44
The Coulombs force between a proton and an
electron is 2.27?1039 times greater than the
gravitational force between them. If the two
forces were equal, what should the size of the
elementary charge be?

1. 1.60 ? 10-19 C
2. 3.36 ? 10-39 C
3. 1.23 ? 10-77 C
4. 2.27 ? 10-39 C
5. 4.41 ? 10-40 C

45
The Coulombs force between a proton and an
electron is 2.27?1039 times greater than the
gravitational force between them. If the two
forces were equal, what should the size of the
elementary charge be?

1. 1.60 ? 10-19 C
2. 3.36 ? 10-39 C
3. 1.23 ? 10-77 C
4. 2.27 ? 10-39 C
5. 4.41 ? 10-40 C

46
A charge 2Q is located at the origin while a
second charge ?Q is located at x a. Where
should a third charge be placed so that the net
force on this third charge is zero?

1. x lt 0
2. 0 lt x lt a
3. x gt a
4. x lt 0 or 0 lt x lt a
5. 0 lt x lt a or x gt a

47
A charge 2Q is located at the origin while a
second charge ?Q is located at x a. Where
should a third charge be placed so that the net
force on this third charge is zero?

1. x lt 0
2. 0 lt x lt a
3. x gt a
4. x lt 0 or 0 lt x lt a
5. 0 lt x lt a or x gt a

48
The force between two very small charged bodies
is found to be F. If the distance between them
is doubled without altering their charges, the
force between them becomes

1. F/2
2. 2F
3. F/4
4. 4F
5. 1/F 2

49
The force between two very small charged bodies
is found to be F. If the distance between them
is doubled without altering their charges, the
force between them becomes

1. F/2
2. 2F
3. F/4
4. 4F
5. 1/F 2

50
The force between two very small charged bodies
is found to be F. If the distance between them
is tripled without altering their charges, the
force between them becomes

1. 9F
2. 3F
3. F/3
4. F/9
5. 1/F 3

51
The force between two very small charged bodies
is found to be F. If the distance between them
is tripled without altering their charges, the
force between them becomes

1. 9F
2. 3F
3. F/3
4. F/9
5. 1/F 3

52
Coulomb's law and Newton's law of gravitation
both involve which of the following?

1. the mass of the particle
2. the charge on the particle
3. permeability
4. permittivity
5. the inverse-square law

53
Coulomb's law and Newton's law of gravitation
both involve which of the following?

1. the mass of the particle
2. the charge on the particle
3. permeability
4. permittivity
5. the inverse-square law

54
Which of the following statements is not true?

1. In nature, electric charge is conserved.
2. The force of repulsion between two like charges
   is directly proportional to the product of the
   square of the charges.
3. The force of repulsion between two like charges
   is inversely proportional to the square of the
   distance separating the charges.
4. Unlike charges attract each other.
5. Like charges repel each other.

55
Which of the following statements is not true?

1. In nature, electric charge is conserved.
2. The force of repulsion between two like charges
   is directly proportional to the product of the
   square of the charges.
3. The force of repulsion between two like charges
   is inversely proportional to the square of the
   distance separating the charges.
4. Unlike charges attract each other.
5. Like charges repel each other.

56
If a positive charge were placed at the origin
(the crossing point of the vertical and
horizontal lines) of the figure, into which
quadrant would it feel a net force?

1. A
2. B
3. C
4. D
5. None, it feels no net force.

57
If a positive charge were placed at the origin
(the crossing point of the vertical and
horizontal lines) of the figure, into which
quadrant would it feel a net force?

1. A
2. B
3. C
4. D
5. None, it feels no net force.

58
If a positive charge were placed at the origin
(the crossing point of the vertical and
horizontal lines) of the figure, into which
quadrant would it feel a net force?

1. A
2. B
3. C
4. D
5. None, it feels no net force.

59
If a positive charge were placed at the origin
(the crossing point of the vertical and
horizontal lines) of the figure, into which
quadrant would it feel a net force?

1. A
2. B
3. C
4. D
5. None, it feels no net force.

60
Chapter 21 The Electric Field I Discrete
Charge Distributions

• Section 21-4 The Electric Field

61
A proton is moving horizontally north in an
electric field that points vertically upward.
The electric force on the proton is

1. zero.
2. upward.
3. downward.
4. to the west.
5. to the east.

62
A proton is moving horizontally north in an
electric field that points vertically upward.
The electric force on the proton is

1. zero.
2. upward.
3. downward.
4. to the west.
5. to the east.

63
An electron is moving horizontally east in an
electric field that points vertically upward.
The electric force on the proton is

1. zero.
2. upward.
3. downward.
4. to the west.
5. to the east.

64
An electron is moving horizontally east in an
electric field that points vertically upward.
The electric force on the proton is

1. zero.
2. upward.
3. downward.
4. to the west.
5. to the east.

65
The SI units of electric fields can be expressed
as

1. C/m2
2. C/s
3. V C
4. N
5. V/m

66
The SI units of electric fields can be expressed
as

1. C/m2
2. C/s
3. V C
4. N
5. V/m

67
Two charges of the same sign are placed a certain
distance apart. There is only one point in space
near them where the electric field is zero.
Which, if any, of the following statements about
that point is true?

1. It cannot be on the line joining the charges.
2. It must be on the line joining the charges and
   between the charges.
3. It must be on the line joining the charges but
   not between the charges.

68
Two charges of the same sign are placed a certain
distance apart. There is only one point in space
near them where the electric field is zero.
Which, if any, of the following statements about
that point is true?

1. It cannot be on the line joining the charges.
2. It must be on the line joining the charges and
   between the charges.
3. It must be on the line joining the charges but
   not between the charges.

69
Three positive and equal charges Q1, Q2, and Q3
are at the corners of an equilateral triangle as
shown. Point P is at the midpoint of the line
between Q1 and Q3. The electric field at P is

1. zero.
2. not zero and is directed along the line from P to
   Q3.
3. not zero and is directed along the line from P to
   Q2.
4. not zero and is directed along the line from Q1
   to Q2.
5. not zero and is directed along the line from P
   away from Q2.

70
Three positive and equal charges Q1, Q2, and Q3
are at the corners of an equilateral triangle as
shown. Point P is at the midpoint of the line
between Q1 and Q3. The electric field at P is

1. zero.
2. not zero and is directed along the line from P to
   Q3.
3. not zero and is directed along the line from P to
   Q2.
4. not zero and is directed along the line from Q1
   to Q2.
5. not zero and is directed along the line from P
   away from Q2.

71
An electric field with a magnitude of 6.0 104
N/C is directed parallel to the positive y axis.
A particle with a charge q 4.8 1019 C is
moving along the x axis with a speed v 3.0
106 m/s. The force on the charge is
approximately

1. 8.6 108 N perpendicular to the xy plane.
2. 2.9 1014 N in the y direction.
3. 8.6 108 N in the x direction.
4. zero.
5. 2.9 1014 N in the x direction.

72
An electric field with a magnitude of 6.0 104
N/C is directed parallel to the positive y axis.
A particle with a charge q 4.8 1019 C is
moving along the x axis with a speed v 3.0
106 m/s. The force on the charge is
approximately

1. 8.6 108 N perpendicular to the xy plane.
2. 2.9 1014 N in the y direction.
3. 8.6 108 N in the x direction.
4. zero.
5. 2.9 1014 N in the x direction.

73
The direction of the electric field at a point is
the same as

1. the direction of the force on a neutron placed at
   that point.
2. the direction of the force on a proton placed at
   that point.
3. the direction of the force on an electron placed
   at that point.
4. the direction of the force on a hydrogen molecule
   placed at that point.
5. None of these is correct.

74
The direction of the electric field at a point is
the same as

1. the direction of the force on a neutron placed at
   that point.
2. the direction of the force on a proton placed at
   that point.
3. the direction of the force on an electron placed
   at that point.
4. the direction of the force on a hydrogen molecule
   placed at that point.
5. None of these is correct.

75
Two point charges of unknown magnitude and sign
are a distance d apart. If the electric field
strength is zero at a point between them on the
line joining them, you can conclude that

1. the charges are equal in magnitude but opposite
   in sign.
2. the charges are equal in magnitude and have the
   same sign.
3. the charges are not necessarily equal in
   magnitude but have opposite signs.
4. the charges are not necessarily equal in
   magnitude but have the same sign.
5. there is not enough information to say anything
   specific about the charges.

76
Two point charges of unknown magnitude and sign
are a distance d apart. If the electric field
strength is zero at a point between them on the
line joining them, you can conclude that

1. the charges are equal in magnitude but opposite
   in sign.
2. the charges are equal in magnitude and have the
   same sign.
3. the charges are not necessarily equal in
   magnitude but have opposite signs.
4. the charges are not necessarily equal in
   magnitude but have the same sign.
5. there is not enough information to say anything
   specific about the charges.

77
Charges Q1 q and Q2 4q are placed as shown.
At which of the five positions indicated by the
lettered dots might the electric field be zero?
78
Charges Q1 q and Q2 4q are placed as shown.
At which of the five positions indicated by the
lettered dots might the electric field be zero?
79
In the diagram, Q1 6.0 mC and Q2 6.0 mC.
The electric field at point (2, 0) is

1. in the positive x direction.
2. in the negative x direction.
3. in the positive y direction.
4. in the negative y direction.
5. zero at this point.

80
In the diagram, Q1 6.0 mC and Q2 6.0 mC.
The electric field at point (2, 0) is

1. in the positive x direction.
2. in the negative x direction.
3. in the positive y direction.
4. in the negative y direction.
5. zero at this point.

81
Two charges Q1 and Q2 are a distance d apart. If
the electric field is zero at a distance of 3d/4
from Q1 (towards Q2), then what is the relation
between Q1 and Q2?

1. Q1 Q2 /9
2. Q1 9Q2
3. Q1 Q2 /3
4. Q1 3Q2
5. Q1 4Q2 /3

82
Two charges Q1 and Q2 are a distance d apart. If
the electric field is zero at a distance of 3d/4
from Q1 (towards Q2), then what is the relation
between Q1 and Q2?

1. Q1 Q2 /9
2. Q1 9Q2
3. Q1 Q2 /3
4. Q1 3Q2
5. Q1 4Q2 /3

83
A conducting sphere with a net charge of ?q and
mass m is suspended from the ceiling by a light
string. A uniform electric field, E, is applied
vertically downward on the sphere. The tension T
in the string is ____ the weight mg.

1. less than
2. equal to
3. greater than

84
A conducting sphere with a net charge of ?q and
mass m is suspended from the ceiling by a light
string. A uniform electric field, E, is applied
vertically downward on the sphere. The tension T
in the string is ____ the weight mg.

1. less than
2. equal to
3. greater than

85
A conducting sphere with a net charge of q-1 ?C
and mass m 1 g is suspended from the ceiling by
a light string. A uniform electric field, E
5000 N/C, is applied vertically downward on the
sphere. The tension T in the string is

1. 5 ? 10-3 N
2. 9.81 ? 10-3 N
3. 4.81 ? 10-3 N
4. 1.48 ? 10-2 N
5. zero

86
A conducting sphere with a net charge of q-1 ?C
and mass m 1 g is suspended from the ceiling by
a light string. A uniform electric field, E
5000 N/C, is applied vertically downward on the
sphere. The tension T in the string is

1. 5 ? 10-3 N
2. 9.81 ? 10-3 N
3. 4.81 ? 10-3 N
4. 1.48 ? 10-2 N
5. zero

87
Chapter 21 The Electric Field I Discrete
Charge Distributions

• Section 21-5 Electric Field Lines

88
The point P is on the axis of a ring of charge,
and all vectors shown lie in the yz plane. The
negatively charged ring lies in the xz plane.
The vector that correctly represents the
direction of the electric field at this point is
89
The point P is on the axis of a ring of charge,
and all vectors shown lie in the yz plane. The
negatively charged ring lies in the xz plane.
The vector that correctly represents the
direction of the electric field at this point is
90
Which of the following statements about electric
field lines is not true?

1. The number of lines leaving a positive charge or
   entering a negative charge is proportional to the
   charge.
2. The lines begin on positive charges and end on
   negative charges.
3. The density of the lines (the number per unit
   area perpendicular to the lines) is proportional
   to the magnitude of the field at that point.
4. Electric field lines cross midway between charges
   that have equal magnitude and sign.
5. The direction of each line indicates the
   direction that a positively charged particle
   would move if placed at that point in the
   electric field.

91
Which of the following statements about electric
field lines is not true?

1. The number of lines leaving a positive charge or
   entering a negative charge is proportional to the
   charge.
2. The lines begin on positive charges and end on
   negative charges.
3. The density of the lines (the number per unit
   area perpendicular to the lines) is proportional
   to the magnitude of the field at that point.
4. Electric field lines cross midway between charges
   that have equal magnitude and sign.
5. The direction of each line indicates the
   direction that a positively charged particle
   would move if placed at that point in the
   electric field.

92
The figure shows the field lines for two charges.
What might be the ratio of the top charge to the
bottom charge?

1. 12
2. ?12
3. 21
4. ?21
5. 2?1

93
The figure shows the field lines for two charges.
What might be the ratio of the top charge to the
bottom charge?

1. 12
2. ?12
3. 21
4. ?21
5. 2?1

94
A square has equal positive charges at three of
its corners, as shown. Which arrow shows the
correct direction of the electric field at point
P?
95
A square has equal positive charges at three of
its corners, as shown. Which arrow shows the
correct direction of the electric field at point
P?
96
A square has equal positive charges at three of
its corners, as shown. Which arrow shows the
correct direction of the electric field at point
P?
97
A square has equal positive charges at three of
its corners, as shown. Which arrow shows the
correct direction of the electric field at point
P?
98
In the figure, the direction of the electric
field at a point equidistant from two charged
bodies A and B is indicated by a vector. Both
charges have the same magnitude. The direction of
the vector indicates that

1. both A and B are positive.
2. both A and B are negative.
3. A is positive and B is negative.
4. B is positive and A is negative.
5. B is negative and A is neutral.

99
In the figure, the direction of the electric
field at a point equidistant from two charged
bodies A and B is indicated by a vector. Both
charges have the same magnitude. The direction of
the vector indicates that

1. both A and B are positive.
2. both A and B are negative.
3. A is positive and B is negative.
4. B is positive and A is negative.
5. B is negative and A is neutral.

100
Chapter 21 The Electric Field I Discrete
Charge Distributions

• Section 21-6 Action of the Electric Field on
  Charges

101
If nonelectric forces are negligible, in a
uniform electric field a proton has

1. a constant velocity in the direction of the
   field.
2. a constant velocity in a direction opposite to
   that of the field.
3. a constant acceleration the direction of the
   field.
4. a constant acceleration in a direction opposite
   to that of the field.
5. a constant acceleration in a direction at right
   angles to the field.

102
If nonelectric forces are negligible, in a
uniform electric field a proton has

1. a constant velocity in the direction of the
   field.
2. a constant velocity in a direction opposite to
   that of the field.
3. a constant acceleration the direction of the
   field.
4. a constant acceleration in a direction opposite
   to that of the field.
5. a constant acceleration in a direction at right
   angles to the field.

103
If nonelectric forces are negligible, a
positively charged particle released from rest in
a nonuniform electric field

1. moves perpendicular to the field with constant
   velocity.
2. moves with constant velocity parallel to the
   field.
3. accelerates in the direction of the field.
4. accelerates perpendicularly to the field.
5. moves only along equipotential lines.

104
If nonelectric forces are negligible, a
positively charged particle released from rest in
a nonuniform electric field

1. moves perpendicular to the field with constant
   velocity.
2. moves with constant velocity parallel to the
   field.
3. accelerates in the direction of the field.
4. accelerates perpendicularly to the field.
5. moves only along equipotential lines.

105
A negatively charged particle moving with speed v
enters a region of uniform electric field E.
Using the direction compass on the right, the
direction of the force on the charge is

1. 1
2. 2
3. 3
4. 4
5. There is no force on the charge.

106
A negatively charged particle moving with speed v
enters a region of uniform electric field E.
Using the direction compass on the right, the
direction of the force on the charge is

1. 1
2. 2
3. 3
4. 4
5. There is no force on the charge.

107
A negatively charged particle moving with speed v
enters a region of uniform electric field E. If
the charge q 1 nC, mass m 1 10?14 kg, speed
v 105 m/s, the electric field strength E 2
105 V/m, and width, w, of the electric field is
0.2 m, what is the speed of the particle when it
emerges from the other side?

1. 1.0 105 m/s
2. 4.0 104 m/s
3. 1.08 105 m/s
4. 1.4 105 m/s
5. 1.8 105 m/s

108
A negatively charged particle moving with speed v
enters a region of uniform electric field E. If
the charge q 1 nC, mass m 1 10?14 kg, speed
v 105 m/s, the electric field strength E 2
105 V/m, and width, w, of the electric field is
0.2 m, what is the speed of the particle when it
emerges from the other side?

1. 1.0 105 m/s
2. 4.0 104 m/s
3. 1.08 105 m/s
4. 1.4 105 m/s
5. 1.8 105 m/s

109
An electric dipole consists of a positive charge
separated from a negative charge of the same
magnitude by a small distance. Which, if any, of
the diagrams best represents the electric field
lines around an electric dipole?

1. 1
2. 2
3. 3
4. 4
5. None of these is correct.

110
An electric dipole consists of a positive charge
separated from a negative charge of the same
magnitude by a small distance. Which, if any, of
the diagrams best represents the electric field
lines around an electric dipole?

1. 1
2. 2
3. 3
4. 4
5. None of these is correct.

111
Two electric dipoles, p1 and p2, are arranged as
shown. The first dipole is not free to rotate but
the second dipole can rotate in any direction.
Which way will p2 rotate? The directions
represent the following 1 clockwise, 2
counter-clockwise, 3 rotate about axis of the
dipole rolling up, and 4 rotate about axis of
the dipole rolling down.

1. 1
2. 2
3. 3
4. 4
5. None of these is correct.

112
Two electric dipoles, p1 and p2, are arranged as
shown. The first dipole is not free to rotate but
the second dipole can rotate in any direction.
Which way will p2 rotate? The directions
represent the following 1 clockwise, 2
counter-clockwise, 3 rotate about axis of the
dipole rolling up, and 4 rotate about axis of
the dipole rolling down.

1. 1
2. 2
3. 3
4. 4
5. None of these is correct.

113
An electric dipole of moment p is placed in a
uniform external electric field. The dipole
moment vector p is in the positive y direction.
The external electric field vector E is in the
positive x direction. When the dipole is aligned
as shown in the diagram, the net torque is in the

1. positive x direction.
2. positive y direction.
3. negative x direction.
4. positive z direction.
5. negative z direction.

114
An electric dipole of moment p is placed in a
uniform external electric field. The dipole
moment vector p is in the positive y direction.
The external electric field vector E is in the
positive x direction. When the dipole is aligned
as shown in the diagram, the net torque is in the

1. positive x direction.
2. positive y direction.
3. negative x direction.
4. positive z direction.
5. negative z direction.