Transcript LQ-Ch

Halliday/Resnick/Walker
Fundamentals of Physics
Classroom Response System Questions
Chapter 22 Electric Fields
Interactive Lecture Questions
22.3.1. Consider what would happen if electric field lines could cross each
other. What would it mean if two electric field lines were to cross?
a) A test charge placed at the intersection of two electric field lines would be
torn apart and travel in two different directions.
b) A test charge placed at the intersection of two electric field lines would
experience a force in two different directions.
c) A positive test charge placed at the intersection of two electric field lines
would follow one of the lines and a negative test charge would follow
the other line.
d) The electric field at the intersection point would be infinitely large.
e) The electric field at the intersection point would be zero.
22.3.1. Consider what would happen if electric field lines could cross each
other. What would it mean if two electric field lines were to cross?
a) A test charge placed at the intersection of two electric field lines would be
torn apart and travel in two different directions.
b) A test charge placed at the intersection of two electric field lines would
experience a force in two different directions.
c) A positive test charge placed at the intersection of two electric field lines
would follow one of the lines and a negative test charge would follow
the other line.
d) The electric field at the intersection point would be infinitely large.
e) The electric field at the intersection point would be zero.
22.4.1. Two negatively-charged objects are located on the x axis, equally distant
from the origin as shown. Consider the electric field at the point P1. How will
that electric field change if a third object with a charge +q is placed at point P2?
Note: the point P2 is the same distance from the origin as the point P1 and the
magnitude of each of the charges is the same.
a) The magnitude of the electric field will
decrease by 25%.
b) The magnitude of the electric field will
increase by 25%.
c) The magnitude of the electric field will
decrease by 50%.
d) The magnitude of the electric field will increase by 50%.
e) The magnitude of the electric field will increase by 100%.
22.4.1. Two negatively-charged objects are located on the x axis, equally distant
from the origin as shown. Consider the electric field at the point P1. How will
that electric field change if a third object with a charge +q is placed at point P2?
Note: the point P2 is the same distance from the origin as the point P1 and the
magnitude of each of the charges is the same.
a) The magnitude of the electric field will
decrease by 25%.
b) The magnitude of the electric field will
increase by 25%.
c) The magnitude of the electric field will
decrease by 50%.
d) The magnitude of the electric field will increase by 50%.
e) The magnitude of the electric field will increase by 100%.
22.4.2. The drawing shows a hollow conducting sphere with a net
positive charge uniformly distributed over its surface. A small
negatively-charged object has been brought near the sphere as
shown. What is the direction of the electric field at the center of the
sphere?
a) There is no electric field at the center of the sphere.
b) to the left
c) to the right
d) upward
e) downward
22.4.2. The drawing shows a hollow conducting sphere with a net
positive charge uniformly distributed over its surface. A small
negatively-charged object has been brought near the sphere as
shown. What is the direction of the electric field at the center of the
sphere?
a) There is no electric field at the center of the sphere.
b) to the left
c) to the right
d) upward
e) downward
22.4.3. At a distance of one centimeter from an electron, the electric
field strength has a value E. At what distance is the electric field
strength equal to E/2?
a) 0.5 cm
b) 1.4 cm
c) 2.0 cm
d) 3.2 cm
e) 4.0 cm
22.4.3. At a distance of one centimeter from an electron, the electric
field strength has a value E. At what distance is the electric field
strength equal to E/2?
a) 0.5 cm
b) 1.4 cm
c) 2.0 cm
d) 3.2 cm
e) 4.0 cm
22.4.4. Consider the electric field lines shown in the drawing. Which of the
following statements correctly describes this situation?
a) The electric field is due to a
positively charged particle.
b) The electric field is due to a
negatively charged particle.
c) The electric field is due to a
positively charged particle and
a negatively charged particle.
d) The electric field is due to
particles that are both charged
either positively or negatively.
22.4.4. Consider the electric field lines shown in the drawing. Which of the
following statements correctly describes this situation?
a) The electric field is due to a
positively charged particle.
b) The electric field is due to a
negatively charged particle.
c) The electric field is due to a
positively charged particle and
a negatively charged particle.
d) The electric field is due to
particles that are both charged
either positively or negatively.
22.4.5. Consider the electric field lines shown in the drawing. Which of the
following statements correctly describes this situation?
a) A and B are both positively
charged particles.
b) A and B are both negatively
charged particles.
c) A is a positively charged
particle and B is a negatively
charged particle.
d) B is a positively charged
particle and A is a negatively
charged particle.
22.4.5. Consider the electric field lines shown in the drawing. Which of the
following statements correctly describes this situation?
a) A and B are both positively
charged particles.
b) A and B are both negatively
charged particles.
c) A is a positively charged
particle and B is a negatively
charged particle.
d) B is a positively charged
particle and A is a negatively
charged particle.
22.4.6. Four charges are located on the corners of a square as shown in
the drawing. What is the direction of the net electric field at the
point labeled P?
a) toward the upper left corner of the square
b) toward the middle of the right side
of the square
c) toward the middle of the bottom
side of the square
d) toward the lower right corner of the square
e) There is no direction. The electric field at P is zero N/C.
22.4.6. Four charges are located on the corners of a square as shown in
the drawing. What is the direction of the net electric field at the
point labeled P?
a) toward the upper left corner of the square
b) toward the middle of the right side
of the square
c) toward the middle of the bottom
side of the square
d) toward the lower right corner of the square
e) There is no direction. The electric field at P is zero N/C.
22.4.7. Four charges are located on the corners of a square as shown in the
drawing. What is the direction of the net electric field at the point
labeled P?
a) toward the upper left corner of the square
b) toward the middle of the right side
of the square
c) toward the middle of the bottom side
of the square
d) toward the lower right corner
of the square
e) There is no direction. The electric field at P is zero N/C.
22.4.7. Four charges are located on the corners of a square as shown in the
drawing. What is the direction of the net electric field at the point
labeled P?
a) toward the upper left corner of the square
b) toward the middle of the right side
of the square
c) toward the middle of the bottom side
of the square
d) toward the lower right corner
of the square
e) There is no direction. The electric field at P is zero N/C.
22.6.1. Consider a line of charge of length L that has a linear charge density  that is
located on the x axis beginning at x = d. Which one of the following
expressions allows one to calculate the electric field at the origin?
 L dx
a) E 
4 0 d x 2
b)
 L 2
E
x dx

0
4 0
c)
 d  L dx
E
4 0 d x 2

d) E 
4 0
L
0
dx
x
 d  L dx
e) E 
4 0 0
x
22.6.1. Consider a line of charge of length L that has a linear charge density  that is
located on the x axis beginning at x = d. Which one of the following
expressions allows one to calculate the electric field at the origin?
 L dx
a) E 
4 0 d x 2
b)
 L 2
E
x dx

0
4 0
c)
 d  L dx
E
4 0 d x 2

d) E 
4 0
L
0
dx
x
 d  L dx
e) E 
4 0 0
x
22.6.2. A uniformly charged rod with a linear charge density  is located along the y
axis as shown. The rod extends to infinity in both directions. Which of the
following expressions gives the magnitude of the electric field at a point P
located a distance d from the rod on the x axis?
a)
E

4 0 x
b)
E

4 0 x 2
c)
E
x
4 0
 x2
d) E 
4 0
e) E = 0 N/C
22.6.2. A uniformly charged rod with a linear charge density  is located along the y
axis as shown. The rod extends to infinity in both directions. Which of the
following expressions gives the magnitude of the electric field at a point P
located a distance d from the rod on the x axis?
a)
E

4 0 x
b)
E

4 0 x 2
c)
E
x
4 0
 x2
d) E 
4 0
e) E = 0 N/C
22.7.1. Two parallel infinite sheets of charge carry equal charge distributions  of
opposite sign. Which of the following expressions gives the electric field in the
region between the infinite sheets?
a)
b)
c)
d)
E   0

0

E
2 0
E

E
4 0
e) This cannot be answered without knowing the distance between the sheets.
22.7.1. Two parallel infinite sheets of charge carry equal charge distributions  of
opposite sign. Which of the following expressions gives the electric field in the
region between the infinite sheets?
a)
b)
c)
d)
E   0

0

E
2 0
E

E
4 0
e) This cannot be answered without knowing the distance between the sheets.
22.8.1. A positively-charged object is released from rest in a region containing a
uniform electric field. Which one of the following statements concerning
the subsequent motion of the object is correct?
a) The object will remain motionless.
b) The object will accelerate to some constant speed and move in the direction
of the electric field.
c) The object will accelerate to some constant speed and move in the direction
opposite that of the electric field.
d) The object will experience a constant acceleration and move in the direction
of the electric field.
e) The object will experience a constant acceleration and move in the direction
opposite that of the electric field.
22.8.1. A positively-charged object is released from rest in a region containing a
uniform electric field. Which one of the following statements concerning
the subsequent motion of the object is correct?
a) The object will remain motionless.
b) The object will accelerate to some constant speed and move in the direction
of the electric field.
c) The object will accelerate to some constant speed and move in the direction
opposite that of the electric field.
d) The object will experience a constant acceleration and move in the direction
of the electric field.
e) The object will experience a constant acceleration and move in the direction
opposite that of the electric field.
22.8.2. Consider the drawing, where the solid lines with arrows
represent the electric field due to the charged object. An electron is
placed at the point P and released from rest. Which of the
following vectors represents the direction of the force, if any, on
the electron?
22.8.2. Consider the drawing, where the solid lines with arrows
represent the electric field due to the charged object. An electron is
placed at the point P and released from rest. Which of the
following vectors represents the direction of the force, if any, on
the electron?
22.8.3. An electron traveling horizontally to the right enters a region
where a uniform electric field is directed downward. What is the
direction of the force exerted on the electron once it has entered
the field?
a) upward
b) downward
c) to the right
d) to the left
e) The force is zero newtons.
22.8.3. An electron traveling horizontally to the right enters a region
where a uniform electric field is directed downward. What is the
direction of the force exerted on the electron once it has entered
the field?
a) upward
b) downward
c) to the right
d) to the left
e) The force is zero newtons.
22.8.4. A positively charged object is located to the left of a negatively
charged object as shown. Electric field lines are shown connecting
the two objects. The five points on the electric field lines are
labeled A, B, C, D, and E. At which one of these points would a
test charge experience the largest force?
a) A
b) B
c) C
d) D
e) E
22.8.4. A positively charged object is located to the left of a negatively
charged object as shown. Electric field lines are shown connecting
the two objects. The five points on the electric field lines are
labeled A, B, C, D, and E. At which one of these points would a
test charge experience the largest force?
a) A
b) B
c) C
d) D
e) E
22.8.5. A positively charged object is located to the left of a negatively
charged object as shown. Electric field lines are shown connecting
the two objects. The five points on the electric field lines are
labeled A, B, C, D, and E. At which one of these points would a
test charge experience the smallest force?
a) A
b) B
c) C
d) D
e) E
22.8.5. A positively charged object is located to the left of a negatively
charged object as shown. Electric field lines are shown connecting
the two objects. The five points on the electric field lines are
labeled A, B, C, D, and E. At which one of these points would a
test charge experience the smallest force?
a) A
b) B
c) C
d) D
e) E
22.8.6. A positively charged object is located to the left of a negatively
charged object as shown. Electric field lines are shown connecting
the two objects. The five points on the electric field lines are
labeled A, B, C, D, and E. At which one of these points would a
test charge experience the largest force?
a) A
b) B
c) C
d) D
e) E
22.8.6. A positively charged object is located to the left of a negatively
charged object as shown. Electric field lines are shown connecting
the two objects. The five points on the electric field lines are
labeled A, B, C, D, and E. At which one of these points would a
test charge experience the largest force?
a) A
b) B
c) C
d) D
e) E
22.8.7. A positively charged object is located to the left of a negatively
charged object as shown. Electric field lines are shown connecting
the two objects. The five points on the electric field lines are
labeled A, B, C, D, and E. At which one of these points would a
test charge experience the smallest force?
a) A
b) B
c) C
d) D
e) E
22.8.7. A positively charged object is located to the left of a negatively
charged object as shown. Electric field lines are shown connecting
the two objects. The five points on the electric field lines are
labeled A, B, C, D, and E. At which one of these points would a
test charge experience the smallest force?
a) A
b) B
c) C
d) D
e) E
22.9.1. A single, positive test charge is brought near a dipole. Under
what circumstances will the force exerted on the test charge by the
de2
dipole be given by F 
?
3
2 0 z
a) the test charge is a much greater charge than that of the dipole
b) the test charge is a much smaller charge than that of the dipole
c) the test charge is very far from the dipole compared to the distance
between the dipole charges
d) the test charge on a line that passes through the dipole axis
e) the test charge on a line is perpendicular to the dipole axis
22.9.1. A single, positive test charge is brought near a dipole. Under
what circumstances will the force exerted on the test charge by the
de2
dipole be given by F 
?
3
2 0 z
a) the test charge is a much greater charge than that of the dipole
b) the test charge is a much smaller charge than that of the dipole
c) the test charge is very far from the dipole compared to the distance
between the dipole charges
d) the test charge on a line that passes through the dipole axis
e) the test charge on a line is perpendicular to the dipole axis