Chapter 26: The Magnetic Field
Section 26-1: The Force Exerted
by a Magnetic Field, and Concept
Checks 26-1 and 26-2
The direction of any magnetic field is specified as
the direction that the north pole of a compass
needle points toward when the needle is aligned in
the field. Suppose that the direction of the
magnetic field were instead specified as the
direction pointed toward by the south pole of a
compass needle aligned in the field. Would the
right-hand rule for force then give the direction of
the magnetic force on the moving positive charge,
or would a left-hand rule be required?
A. The right-hand rule would still work.
B. A left-hand rule would be required.
The direction of any magnetic field is specified as
the direction that the north pole of a compass
needle points toward when the needle is aligned in
the field. Suppose that the direction of the
magnetic field were instead specified as the
direction pointed toward by the south pole of a
compass needle aligned in the field. Would the
right-hand rule for force then give the direction of
the magnetic force on the moving positive charge,
or would a left-hand rule be required?
A. The right-hand rule would still work.
B. A left-hand rule would be required.
The particle in the figure
A. is positively charged.
B. is negatively charged.
C. could be negatively or
positively charged.
The particle in the figure
A. is positively charged.
B. is negatively
charged.
C. could be negatively or
positively charged.
The phenomenon of magnetism is best
understood in terms of
A. the existence of magnetic poles.
B. the magnetic fields associated with
the movement of charged particles.
C. gravitational forces between nuclei
and orbital electrons.
D. electrical fluids.
E. None of these is correct.
The phenomenon of magnetism is best
understood in terms of
A. the existence of magnetic poles.
B. the magnetic fields associated
with the movement of charged
particles.
C. gravitational forces between nuclei
and orbital electrons.
D. electrical fluids.
E. None of these is correct.
The left diagram shows a positively
charged particle is moving with velocity v in
a magnetic field B. Using the arrows in the
right diagram, what is the direction of the
magnetic force on the particle?
The left diagram shows a positively
charged particle is moving with velocity v in
a magnetic field B. Using the arrows in the
right diagram, what is the direction of the
magnetic force on the particle?
The left diagram shows a force F on a
negatively charged particle moving a
magnetic field B. Using the arrows in the
right diagram, what is the direction of the
velocity of the particle?
The left diagram shows a force F on a
negatively charged particle moving a
magnetic field B. Using the arrows in the
right diagram, what is the direction of the
velocity of the particle?
If the magnetic field vector is directed
toward the north and a positively charged
particle is moving toward the east, what is
the direction of the magnetic force on the
particle?
A. up
B. west
C. south
D. down
E. east
If the magnetic field vector is directed
toward the north and a positively charged
particle is moving toward the east, what is
the direction of the magnetic force on the
particle?
A. up
B. west
C. south
D. down
E. east
A positively charged particle is moving
northward in a magnetic field. The
magnetic force on the particle is toward
the northeast. What is the direction of the
magnetic field?
A. up
B. northeast
C. southwest
D. down
E. This situation cannot exist.
A positively charged particle is moving
northward in a magnetic field. The
magnetic force on the particle is toward
the northeast. What is the direction of the
magnetic field?
A. up
B. northeast
C. southwest
D. down
E. This situation cannot exist.
The SI unit of magnetic field is the tesla
(T). This is equivalent to
A. N · s/(C · m)
B. N · C/(s · m)
C. N · m/s2
D. C/(A · s)
E. None of these is correct.
The SI unit of magnetic field is the tesla
(T). This is equivalent to
A. N · s/(C · m)
B. N · C/(s · m)
C. N · m/s2
D. C/(A · s)
E. None of these is correct.
The region of space around a moving
proton contains
A. a magnetic field only.
B. an electric field only.
C. both an electric and a magnetic field.
D. neither an electric nor a magnetic
field.
The region of space around a moving
proton contains
A. a magnetic field only.
B. an electric field only.
C. both an electric and a magnetic
field.
D. neither an electric nor a magnetic
field.
The magnetic force on a charged particle
A. depends on the sign of the charge on
the particle.
B. depends on the velocity of the particle.
C. depends on the magnetic field at the
particle's instantaneous position.
D. is at right angles to both the velocity
and the direction of the magnetic field.
E. is described by all of these.
The magnetic force on a charged particle
A. depends on the sign of the charge on
the particle.
B. depends on the velocity of the particle.
C. depends on the magnetic field at the
particle's instantaneous position.
D. is at right angles to both the velocity
and the direction of the magnetic field.
E. is described by all of these.
An electron is traveling horizontally east
in the magnetic field of the earth near the
equator. The direction of the force on the
electron is
A. zero
B. north
C. south
D. upward
E. downward
An electron is traveling horizontally east
in the magnetic field of the earth near the
equator. The direction of the force on the
electron is
A. zero
B. north
C. south
D. upward
E. downward
A current I flows in a wire that is oriented
as shown. Which of the vectors represent
the magnetic field that results in a
maximum force on the wire?
A current I flows in a wire that is oriented
as shown. Which of the vectors represent
the magnetic field that results in a
maximum force on the wire?
A wire of length L carries a current I, going from
West to East, in the presence of a magnetic field
B pointing vertically up. The wire moves a
distance d to the south. The work done by the
magnetic force on the moving charges is
A. +ILBd
B. -ILBd
C. +IL2B/d
D. -IL2B/d
E. zero
A wire of length L carries a current I, going from
West to East, in the presence of a magnetic field
B pointing vertically up. The wire moves a
distance d to the south. The work done by the
magnetic force on the moving charges is
A. +ILBd
B. -ILBd
C. +IL2B/d
D. -IL2B/d
E. zero
Chapter 26: The Magnetic Field
Section 26-2: Motion of a Point
Charge in a Magnetic Field
A particle with charge q and mass m is
moving with speed v in the +x direction
enters a magnetic field of strength B pointing
in the +y direction. The work done by the
magnetic force on the particle as it travels
one semi-circle is
A. mqvB
B. mv2
C. qvB
D. zero
E. mv/qB
A particle with charge q and mass m is
moving with speed v in the +x direction
enters a magnetic field of strength B pointing
in the +y direction. The work done by the
magnetic force on the particle as it travels
one semi-circle is
A. mqvB
B. mv2
C. qvB
D. zero
E. mv/qB
A positively charged particle moves with speed v in
the positive x direction. A uniform magnetic field of
magnitude B exists in the negative z direction. You
want to balance the magnetic force with an electric
field so that the particle will continue along a
straight line. The electric field should be in the
A. positive x direction.
B. positive z direction.
C. negative y direction.
D. negative x direction.
E. negative z direction.
A positively charged particle moves with speed v in
the positive x direction. A uniform magnetic field of
magnitude B exists in the negative z direction. You
want to balance the magnetic force with an electric
field so that the particle will continue along a
straight line. The electric field should be in the
A. positive x direction.
B. positive z direction.
C. negative y direction.
D. negative x direction.
E. negative z direction.
A 7Li nucleus with a charge of +3e and a mass of 7
u and a proton with a charge of +e and a mass of
1 u are both moving in a plane perpendicular to a
magnetic field . The two particles have the same
momentum. The ratio of the radius of curvature of
the path of the proton (Rp) to that of the 7Li nucleus
(RLi) is
A.
Rp/RLi = 3
B.
Rp/RLi = 1/3
C. Rp/RLi = 1/7
D. Rp/RLi = 3/7
E.
None of these is correct.
A 7Li nucleus with a charge of +3e and a mass of 7
u and a proton with a charge of +e and a mass of
1 u are both moving in a plane perpendicular to a
magnetic field . The two particles have the same
momentum. The ratio of the radius of curvature of
the path of the proton (Rp) to that of the 7Li nucleus
(RLi) is
A. Rp/RLi = 3
B.
Rp/RLi = 1/3
C. Rp/RLi = 1/7
D. Rp/RLi = 3/7
E.
None of these is correct.
A doubly ionized oxygen atom 16O++ is moving in
the same uniform magnetic field as an alpha
particle. The velocities of both particles are at right
angles to the magnetic field. The paths of the
particles have the same radius of curvature. The
ratio of the energy of the alpha particle to that of
the 16O2+ ion is
A. Ea /EO = 1/1
B. Ea /EO = 1/4
C. Ea /EO = 1/16
D. Ea /EO = 4/1
E. None of these is correct.
A doubly ionized oxygen atom 16O++ is moving in
the same uniform magnetic field as an alpha
particle. The velocities of both particles are at right
angles to the magnetic field. The paths of the
particles have the same radius of curvature. The
ratio of the energy of the alpha particle to that of
the 16O2+ ion is
A. Ea /EO = 1/1
B. Ea /EO = 1/4
C. Ea /EO = 1/16
D. Ea /EO = 4/1
E. None of these is correct.
Electrons travel at an initial velocity v0. They pass
through a set of deflection plates, between which
there exists an electric field which deflects them
upwards toward point b. In which direction should a
magnetic field be applied so that the electrons land
undeflected at a?
Electrons travel at an initial velocity v0. They pass
through a set of deflection plates, between which
there exists an electric field which deflects them
upwards toward point b. In which direction should a
magnetic field be applied so that the electrons land
undeflected at a?
An electron moves with speed v
in the positive x direction. A
uniform magnetic field of
magnitude B exists in the positive
y direction. As the electron
moves through this region, it is
A. deflected in the positive y direction.
B. deflected in the positive z direction.
C. deflected in the negative y direction.
D. deflected in the negative z direction.
E. undeviated in its motion.
An electron moves with speed v
in the positive x direction. A
uniform magnetic field of
magnitude B exists in the positive
y direction. As the electron
moves through this region, it is
A. deflected in the positive y direction.
B. deflected in the positive z direction.
C. deflected in the negative y direction.
D. deflected in the negative z direction.
E. undeviated in its motion.
All of the charged particles that pass
through a certain set of crossed electric
and magnetic fields without deflection
must have the same
A. mass.
B. speed.
C. momentum.
D. energy.
E. charge-to-mass ratio.
All of the charged particles that pass
through a certain set of crossed electric
and magnetic fields without deflection
must have the same
A. mass.
B. speed.
C. momentum.
D. energy.
E. charge-to-mass ratio.
A small positively charged body is moving
horizontally and westward. If it enters a
uniform horizontal magnetic field that is
directed from north to south, the body is
deflected
A. upward.
B. downward.
C. toward the north.
D. toward the south.
E. not at all.
A small positively charged body is moving
horizontally and westward. If it enters a
uniform horizontal magnetic field that is
directed from north to south, the body is
deflected
A. upward.
B. downward.
C. toward the north.
D. toward the south.
E. not at all.
A positively charged particle is
moving through uniform fields
and , which are directed in the
positive x and positive y
directions, respectively. If there
is no resultant force on the
particle, then its velocity is in the
A. positive x direction.
B. positive y direction.
C. negative x direction.
D. positive z direction.
E. negative z direction.
A positively charged particle is
moving through uniform fields
and , which are directed in the
positive x and positive y
directions, respectively. If there
is no resultant force on the
particle, then its velocity is in the
A. positive x direction.
B. positive y direction.
C. negative x direction.
D. positive z direction.
E. negative z direction.
A uniform magnetic field is
parallel to and in the direction
of the positive z axis. For an
electron to enter this field and
not be deflected by the field,
the electron must be traveling
in which direction?
A. any direction as long as it is in the xy plane.
B. any direction as long as it is in the xz plane.
C. along the x axis.
D. along the y axis.
E. along the z axis.
A uniform magnetic field is
parallel to and in the direction
of the positive z axis. For an
electron to enter this field and
not be deflected by the field,
the electron must be traveling
in which direction?
A. any direction as long as it is in the xy plane.
B. any direction as long as it is in the xz plane.
C. along the x axis.
D. along the y axis.
E. along the z axis.
The track ABC in the
figure is a reproduction
of the path of a charged
particle in a cloud
chamber. If the magnetic
field is perpendicular to
this sheet of paper and
directed into the paper,
the particle
A. has a positive charge and has moved from C to A.
B. has a negative charge and has moved from C to A.
C. has a positive charge and has moved from A to C.
D. has a negative charge and has moved from A to C.
The track ABC in the
figure is a reproduction
of the path of a charged
particle in a cloud
chamber. If the magnetic
field is perpendicular to
this sheet of paper and
directed into the paper,
the particle
A. has a positive charge and has moved from C to A.
B. has a negative charge and has moved from C
to A.
C. has a positive charge and has moved from A to C.
D. has a negative charge and has moved from A to C.
Chapter 26: The Magnetic Field
Section 26-3: Torques on Current
Loops and Magnets
A circular current loop lies in the xy plane and
has radius R = 10 cm. The loop has 20 turns and
carries a current I = 4 A. The magnetic dipole of
the loop is
z
ˆ
A.  2.51 A  m k
B. 2.51 A  m kˆ
B
C.  0.126 A  m kˆ
D. 0.126 A  m kˆ
E.  0.628 A  m kˆ

x
R
I
y
A circular current loop lies in the xy plane and
has radius R = 10 cm. The loop has 20 turns and
carries a current I = 4 A. The magnetic dipole of
the loop is
z
ˆ
A.  2.51 A  m k
B. 2.51 A  m kˆ
B
C.  0.126 A  m kˆ
D. 0.126 A  m kˆ
E.  0.628 A  m kˆ

x
R
I
y
A rectangle is bent on two sides at 90 so that
one end lies along the xy plane while the other
end lies along the xz plane. The length of each
bent portion is illustrated on the Figure. A
current I flows through the loop. The magnetic
dipole of the rectangle is
z
A. abI (iˆ  ˆj )
B. abI ( ˆj  kˆ)
C.  abI (iˆ  ˆj )
D.  abI ( ˆj  kˆ)
I
a
E. None of these is correct.
x
b
a
y
A rectangle is bent on two sides at 90 so that
one end lies along the xy plane while the other
end lies along the xz plane. The length of each
bent portion is illustrated on the Figure. A
current I flows through the loop. The magnetic
dipole of the rectangle is
z
A. abI (iˆ  ˆj )
B. abI ( ˆj  kˆ)
C.  abI (iˆ  ˆj )
D.  abI ( ˆj  kˆ)
I
a
E. None of these is correct.
x
b
a
y
Chapter 26: The Magnetic Field
Section 26-4: The Hall Effect
A current I passes through a slab of metal in
the presence of a magnetic field B. Between
which two sides does a Hall voltage
develop? Write the side with the higher
potential first.
A. a and b
B. c and d
C. e and f
D. b and a
E. d and c .
e
I
d
a
c
f
B
b
A current I passes through a slab of metal in
the presence of a magnetic field B. Between
which two sides does a Hall voltage
develop? Write the side with the higher
potential first.
A. a and b
B. c and d
C. e and f
D. b and a
E. d and c .
e
I
d
a
c
f
B
b
The rectangular aluminum
strip in the figure is in a
uniform magnetic field, B.
The current I is flowing
perpendicular to surface 1.
Positive charges will
accumulate on
A. surface 1.
B. surface 2.
C. surface 3.
D. the surface opposite surface 2.
E. none of these surfaces.
The rectangular aluminum
strip in the figure is in a
uniform magnetic field, B.
The current I is flowing
perpendicular to surface 1.
Positive charges will
accumulate on
A. surface 1.
B. surface 2.
C. surface 3.
D. the surface opposite surface 2.
E. none of these surfaces.