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```					    Halliday/Resnick/Walker
Fundamentals of Physics 8th edition

Classroom Response System Questions
Chapter 22 Electric Fields

22.2.1. Which one of the following statements concerning the electric field is
false?

a) The SI unit of the electric field is the newton per meter (N/m)

b) The electric field is a vector quantity.

c) At a given point, a charged particle will experience a force, if an electric
field is present at that location.

d) If a positively-charged particle is placed at a location where the electric
field is directed due north, it will be accelerated due north.

e) The magnitude of the electric field at a particular location due to a
particular charged particle is inversely proportional to the distance of the
particle from that location.
22.2.1. Which one of the following statements concerning the electric field is
false?

a) The SI unit of the electric field is the newton per meter (N/m)

b) The electric field is a vector quantity.

c) At a given point, a charged particle will experience a force, if an electric
field is present at that location.

d) If a positively-charged particle is placed at a location where the electric
field is directed due north, it will be accelerated due north.

e) The magnitude of the electric field at a particular location due to a
particular charged particle is inversely proportional to the distance of the
particle from that location.
22.2.2. Which of the following combination of units are those for the
strength of the electric field?

a) kg  m 2
C  s2

b) N  m
C

c) kg  m
Cs

N
d)
C

Cm
e)
s
22.2.2. Which of the following combination of units are those for the
strength of the electric field?

a) kg  m 2
C  s2

b) N  m
C

c) kg  m
Cs

N
d)
C

Cm
e)
s
22.2.3. Which one of the following statements best describes the concept of the
electric field?

a) The electric field is a vector quantity that is the reaction force of electrons.

b) The electric field at each point is the potential energy of a test charge divided
by the amount of the test charge.

c) The electric field is a distribution of vectors at points due to the presence of
one or more charged objects.

d) The electric field is a scalar quantity related to the total amount of charge on
one or more charged objects.

e) The electric field is a scalar field, which has a magnitude at each given point,
similar to the temperature or pressure field.
22.2.3. Which one of the following statements best describes the concept of the
electric field?

a) The electric field is a vector quantity that is the reaction force of electrons.

b) The electric field at each point is the potential energy of a test charge divided
by the amount of the test charge.

c) The electric field is a distribution of vectors at points due to the presence of
one or more charged objects.

d) The electric field is a scalar quantity related to the total amount of charge on
one or more charged objects.

e) The electric field is a scalar field, which has a magnitude at each given point,
similar to the temperature or pressure field.
22.3.1. Which of the following statements concerning electric field lines is
false?

a) Electric field lines between two charged particles are often curved.

b) Electric field lines are a method proposed by Michael Faraday to map the
electric field at various locations.

c) Electric field lines can be used to indicate the local magnitude of the
electric field.

d) Electric field lines are always directed radially away from a positively-
charged particle.

e) An electric field line indicates the direction of the force on an electron
placed on the line.
22.3.1. Which of the following statements concerning electric field lines is
false?

a) Electric field lines between two charged particles are often curved.

b) Electric field lines are a method proposed by Michael Faraday to map the
electric field at various locations.

c) Electric field lines can be used to indicate the local magnitude of the
electric field.

d) Electric field lines are always directed radially away from a positively-
charged particle.

e) An electric field line indicates the direction of the force on an electron
placed on the line.
22.3.2. Consider the following observations: (1) electric field lines are
drawn connecting two point charges labeled A and B, (2) charge A
is due north of charge B, and (3) a proton placed at the mid-point
on a line connecting the two point charges travels due south.
Which one of the following statements correctly indicates the signs
of the two charges?

a) Charge A is positive and charge B is negative.

b) Charge A is positive and charge B is positive.

c) Charge A is negative and charge B is positive.

d) Charge A is negative and charge B is negative.
22.3.2. Consider the following observations: (1) electric field lines are
drawn connecting two point charges labeled A and B, (2) charge A
is due north of charge B, and (3) a proton placed at the mid-point
on a line connecting the two point charges travels due south.
Which one of the following statements correctly indicates the signs
of the two charges?

a) Charge A is positive and charge B is negative.

b) Charge A is positive and charge B is positive.

c) Charge A is negative and charge B is positive.

d) Charge A is negative and charge B is negative.
22.3.3. The direction of the electric field is the same as which of the
following properties related to a test charge?

a) velocity of the test charge

b) force on a positive test charge

c) acceleration of a negative test charge

d) displacement of a moving test charge

e) None of the above choices are related to the direction of the electric
field.
22.3.3. The direction of the electric field is the same as which of the
following properties related to a test charge?

a) velocity of the test charge

b) force on a positive test charge

c) acceleration of a negative test charge

d) displacement of a moving test charge

e) None of the above choices are related to the direction of the electric
field.
22.3.4. Complete the following statement: Electric field lines depend
on

a) the direction of the electric field.

b) the strength of the electric field.

c) the force exerted on a test charge.

d) All of the above choices correctly complete the statement.

e) None of the choices correctly complete the statement.
22.3.4. Complete the following statement: Electric field lines depend
on

a) the direction of the electric field.

b) the strength of the electric field.

c) the force exerted on a test charge.

d) All of the above choices correctly complete the statement.

e) None of the choices correctly complete the statement.
22.4.1. Which one of the following statements best describes the electric field at
a distance r from the electron?

a) The electric field is directed toward the electron and has a magnitude of ke/r2.

b) The electric field is directed away from the electron and has a magnitude of
ke/r2.

c) The electric field is directed toward the electron and has a magnitude of ke/r.

d) The electric field is directed away from the electron and has a magnitude of
ke/r.

e) The electric field is directed toward the electron and has a magnitude of ke2/r.
22.4.1. Which one of the following statements best describes the electric field at
a distance r from the electron?

a) The electric field is directed toward the electron and has a magnitude of ke/r2.

b) The electric field is directed away from the electron and has a magnitude of
ke/r2.

c) The electric field is directed toward the electron and has a magnitude of ke/r.

d) The electric field is directed away from the electron and has a magnitude of
ke/r.

e) The electric field is directed toward the electron and has a magnitude of ke2/r.
22.4.2. Consider the field lines shown in the drawing. Which one of the following
statements concerning this situation is true?

a) These field lines are those for a
positively charged particle.

b) These field lines are those for a
negatively charged particle.

c) These field lines are those for a
positively charged particle and a
negatively charged particle.

d) These field lines are those for two
positively charged particles.

e) These field lines are those for two negatively charged particles.
22.4.2. Consider the field lines shown in the drawing. Which one of the following
statements concerning this situation is true?

a) These field lines are those for a
positively charged particle.

b) These field lines are those for a
negatively charged particle.

c) These field lines are those for a
positively charged particle and a
negatively charged particle.

d) These field lines are those for two
positively charged particles.

e) These field lines are those for two negatively charged particles.
22.4.3. Consider the field lines shown in the drawing. Which one of
the following statements concerning this situation is true?

a) A is a positively charged particle
and B is negatively charged.

b) B is a positively charged particle
and A is negatively charged.

c) A and B are both positively
charged.

d) A and B are both negatively
charged.
22.4.3. Consider the field lines shown in the drawing. Which one of
the following statements concerning this situation is true?

a) A is a positively charged particle
and B is negatively charged.

b) B is a positively charged particle
and A is negatively charged.

c) A and B are both positively
charged.

d) A and B are both negatively
charged.
22.5.1. Which one of the following expressions gives the correct
relationship between the electric field strength E and the distance r
from an electric dipole?
1
a) E 
r
1
b) E 
r2
1
c) E  3
r
d) E  r

e) E  r2
22.5.1. Which one of the following expressions gives the correct
relationship between the electric field strength E and the distance r
from an electric dipole?
1
a) E 
r
1
b) E 
r2
1
c) E  3
r
d) E  r

e) E  r2
22.5.2. Why does the electric field due to a dipole decrease more
rapidly with increasing distance than that for a single charge?

a) The two charges in the dipole are separated by some distance.

b) Because there are two charges in the dipole, the electric field has
one-half the field strength of a single charge.

c) Any given point is closer to one of the charges of the dipole than to
the other.

d) The total charge of the dipole is neutral (zero).

e) Dipoles do not produce a significant electric field.
22.5.2. Why does the electric field due to a dipole decrease more
rapidly with increasing distance than that for a single charge?

a) The two charges in the dipole are separated by some distance.

b) Because there are two charges in the dipole, the electric field has
one-half the field strength of a single charge.

c) Any given point is closer to one of the charges of the dipole than to
the other.

d) The total charge of the dipole is neutral (zero).

e) Dipoles do not produce a significant electric field.
22.5.3. Which one of the following statements concerning the electric dipole
moment is false?

a) The dipole moment is a scalar quantity.

b) The dipole moment has units of Cm.

c) The dipole moment combines two intrinsic properties of an electric
dipole, the distance between the charges and the amount of charge on
each object.

d) The dipole moment is directed from the negative charge toward the
positive charge of the dipole.

e) The direction of the dipole moment is used to specify the orientation of
the dipole.
22.5.3. Which one of the following statements concerning the electric dipole
moment is false?

a) The dipole moment is a scalar quantity.

b) The dipole moment has units of Cm.

c) The dipole moment combines two intrinsic properties of an electric
dipole, the distance between the charges and the amount of charge on
each object.

d) The dipole moment is directed from the negative charge toward the
positive charge of the dipole.

e) The direction of the dipole moment is used to specify the orientation of
the dipole.
22.6.1. Consider the following hypothetical situation: An infinitely
long line of charge is located along the central axis of an infinitely
long hollow cylinder of charge. Which of the following statements
concerning the force on the line of charge is true?

a) The force on the line of charge is infinite.

b) The force on the line of charge is zero newtons.

c) The force depends on the radius of the cylinder. It will be larger if

d) The force depends on the radius of the cylinder. It will be smaller
if the cylinder radius is large.
22.6.1. Consider the following hypothetical situation: An infinitely
long line of charge is located along the central axis of an infinitely
long hollow cylinder of charge. Which of the following statements
concerning the force on the line of charge is true?

a) The force on the line of charge is infinite.

b) The force on the line of charge is zero newtons.

c) The force depends on the radius of the cylinder. It will be larger if

d) The force depends on the radius of the cylinder. It will be smaller
if the cylinder radius is large.
22.6.2. Which one of the following statements concerning charge
distributions is false?

a) Charge distributions consist of a very large number of closely spaced
charges.

b) Charge distributions may be uniform arrangements of charges along a
line, over a surface, or throughout a volume.

c) Calculus provides important tools for determining electric fields due to
charge distributions.

d) Charge distributions are treated as being composed of discrete charges.

e) In dealing with charge distributions, it is often more useful to speak in
terms of a charge density rather than the total charge.
22.6.2. Which one of the following statements concerning charge
distributions is false?

a) Charge distributions consist of a very large number of closely spaced
charges.

b) Charge distributions may be uniform arrangements of charges along a
line, over a surface, or throughout a volume.

c) Calculus provides important tools for determining electric fields due to
charge distributions.

d) Charge distributions are treated as being composed of discrete charges.

e) In dealing with charge distributions, it is often more useful to speak in
terms of a charge density rather than the total charge.
22.6.3. Consider the drawing which shows a uniform ring of charge of radius R.
Which of the following expressions gives the correct dependence of the
electric field at point P located on the z axis, where z >> R?
1
a) E 
z
1
b) E 
z2
1
c) E 
z3

d)   Ez

e) E  z 2
22.6.3. Consider the drawing which shows a uniform ring of charge of radius R.
Which of the following expressions gives the correct dependence of the
electric field at point P located on the z axis, where z >> R?
1
a) E 
z
1
b) E 
z2
1
c) E 
z3

d)   Ez

e) E  z 2
22.7.1. Which of the following expressions gives the electric field due to an infinite
sheet of charge with a uniform charge density ?


a) E 
2r

b) E 
2r 2
2
c) E 
 0r 3

d) E 
2 0
 2
e) E       r
0
22.7.1. Which of the following expressions gives the electric field due to an infinite
sheet of charge with a uniform charge density ?


a) E 
2r

b) E 
2r 2
2
c) E 
 0r 3

d) E 
2 0
 2
e) E       r
0
22.8.1. Two positively charged particles are in fixed locations on the x axis. A test charge
that is free to move about the x-y plane is placed at the mid-point between the two
positively charged particles. If the test charge is held stationary at the mid-point and
then released, it remains stationary. Which of the following is the best explanation
for this behavior?

a) The test charge is at a point of stable equilibrium for both the x and y directions.

b) The test charge is at a point of stable equilibrium for the x direction, but not for the y
direction.

c) The test charge is at a point of stable equilibrium for the y direction, but not for the x
direction.

d) The test charge is at a point of unstable equilibrium for both the x direction and the y
direction.

e) No forces are acting on the test charge.
22.8.1. Two positively charged particles are in fixed locations on the x axis. A test charge
that is free to move about the x-y plane is placed at the mid-point between the two
positively charged particles. If the test charge is held stationary at the mid-point and
then released, it remains stationary. Which of the following is the best explanation
for this behavior?

a) The test charge is at a point of stable equilibrium for both the x and y directions.

b) The test charge is at a point of stable equilibrium for the x direction, but not for the y
direction.

c) The test charge is at a point of stable equilibrium for the y direction, but not for the x
direction.

d) The test charge is at a point of unstable equilibrium for both the x direction and the y
direction.

e) No forces are acting on the test charge.
22.9.1. A dipole is located within a uniform electric field and aligned perpendicular to the
field. Why is the electrostatic potential energy is equal to zero joules in this
situation?

a) There is no force acting on the dipole. Only a torque is acting on it.

b) There is no torque acting on the dipole when the dipole is parallel or antiparallel to the
field, so when the dipole is perpendicular, the potential energy must be zero joules.

c) Because the zero potential energy position is arbitrary, you may choose it to be
anything.

d) If the dipole is parallel or antiparallel to the electric field it must have correspondingly
opposite signs, therefore when it is perpendicular to the field, the energy must be zero
joules.

e) Dipoles have no interaction with electric fields since their net charge is zero coulombs,
so the potential energy is always zero joules.
22.9.1. A dipole is located within a uniform electric field and aligned perpendicular to the
field. Why is the electrostatic potential energy is equal to zero joules in this
situation?

a) There is no force acting on the dipole. Only a torque is acting on it.

b) There is no torque acting on the dipole when the dipole is parallel or antiparallel to the
field, so when the dipole is perpendicular, the potential energy must be zero joules.

c) Because the zero potential energy position is arbitrary, you may choose it to be
anything.

d) If the dipole is parallel or antiparallel to the electric field it must have correspondingly
opposite signs, therefore when it is perpendicular to the field, the energy must be zero
joules.

e) Dipoles have no interaction with electric fields since their net charge is zero coulombs,
so the potential energy is always zero joules.
22.9.2. Consider the dipole shown in a uniform electric field. Which of the
following occurs as the dipole aligns itself with the electric field?

a) The electric field breaks the dipole
into two separate charges.

b) The total energy of the dipole and
electric field decreases.

c) The potential energy of the electric
field and the dipole does not change.

d) The potential energy of the electric
field and the dipole increases.

e) The potential energy of the electric field and the dipole decreases.
22.9.2. Consider the dipole shown in a uniform electric field. Which of the
following occurs as the dipole aligns itself with the electric field?

a) The electric field breaks the dipole
into two separate charges.

b) The total energy of the dipole and
electric field decreases.

c) The potential energy of the electric
field and the dipole does not change.

d) The potential energy of the electric
field and the dipole increases.

e) The potential energy of the electric field and the dipole decreases.

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