Download A point charge is moving with speed 2 ´ 107 m/s along the x axis. At t

Chapter 27: Sources of the Magnetic
Field
Section 27-1: The Magnetic Field of
Moving Point Charges
A point charge is moving with constant speed 2
×107 m/s along the x axis. It creates a
magnetic field as it travels through a region
where there is no external magnetic field. At t =
0, the charge is at x = 0 m and the magnitude
of the magnetic field at x = 4 m is B0. The
magnitude of the magnetic field at x = 4m
when t = 0.1 s is
A. B0/2
B. B0
C. B0/4
D. 2B0
E. 4B0
A point charge is moving with constant speed 2
×107 m/s along the x axis. It creates a
magnetic field as it travels through a region
where there is no external magnetic field. At t =
0, the charge is at x = 0 m and the magnitude
of the magnetic field at x = 4 m is B0. The
magnitude of the magnetic field at x = 4m
when t = 0.1 s is
A. B0/2
B. B0
C. B0/4
D. 2B0
E. 4B0
The top diagram shows the velocity of a
positively charged particle. Which arrow
best represents the direction of the
magnetic field due to the moving charge
at r ?
The top diagram shows the velocity of a
positively charged particle. Which arrow
best represents the direction of the
magnetic field due to the moving charge
at r ?
The magnitude of the magnetic field due to the
presence of a charged body
A. varies directly with the speed of the body.
B. varies directly with the charge carried by the
body.
C. varies inversely with the square of the
distance between the charged body and the
field point.
D. depends on the magnetic properties of the
space between the charged body and the
field point.
E. is described by all of these.
The magnitude of the magnetic field due to the
presence of a charged body
A. varies directly with the speed of the body.
B. varies directly with the charge carried by the
body.
C. varies inversely with the square of the
distance between the charged body and the
field point.
D. depends on the magnetic properties of the
space between the charged body and the
field point.
E. is described by all of these.
A positively charged body is moving in the
negative z direction as shown. What is the
direction of the magnetic field due to the
motion of this charged body at point P?
A positively charged body is moving in the
negative z direction as shown. What is the
direction of the magnetic field due to the
motion of this charged body at point P?
A positively charged body is moving in the positive x
direction as shown. The direction of the magnetic field at
the origin due to the motion of this charged body is
A.
B.
C.
D.
E.
1
2
3
4
None of these is correct, as this charged body does not
create a magnetic field along the axis of its motion.
A positively charged body is moving in the positive x
direction as shown. The direction of the magnetic field at
the origin due to the motion of this charged body is
A.
B.
C.
D.
E.
1
2
3
4
None of these is correct, as this charged body does
not create a magnetic field along the axis of its
motion.
At the instant the positively
charged body is at the origin, the
magnetic field at point P due to
the motion of this charged body
is in the negative x direction. The
charged body must be moving
A. in the negative z direction.
B. in the positive y direction.
C. in the positive x direction.
D. in the negative y direction.
E. in the positive z direction.
At the instant the positively
charged body is at the origin, the
magnetic field at point P due to
the motion of this charged body
is in the negative x direction. The
charged body must be moving
A. in the negative z direction.
B. in the positive y direction.
C. in the positive x direction.
D. in the negative y direction.
E. in the positive z
direction.
At the instant the negatively
charged body is at the origin, the
magnetic field at point P due to
its motion is in the negative x
direction. The charged body
must be moving
A. in the negative z direction.
B. in the positive y direction.
C. in the positive x direction.
D. in the negative y direction.
E. in the positive z direction.
At the instant the negatively
charged body is at the origin, the
magnetic field at point P due to
its motion is in the negative x
direction. The charged body
must be moving
A. in the negative z
direction.
B. in the positive y direction.
C. in the positive x direction.
D. in the negative y direction.
E. in the positive z direction.
Two positively charged bodies are moving in
opposite directions on parallel paths that lie in the
xz plane. Their speeds are equal and their
trajectories are equidistant from the x axis. The
magnetic field at the origin, due to the motion of
these charged bodies will be
A. in the +x direction.
B. in the +y direction.
C. in the −y direction.
D. in the +z direction.
E. zero.
Two positively charged bodies are moving in
opposite directions on parallel paths that lie in the
xz plane. Their speeds are equal and their
trajectories are equidistant from the x axis. The
magnetic field at the origin, due to the motion of
these charged bodies will be
A. in the +x direction.
B. in the +y direction.
C. in the −y direction.
D. in the +z direction.
E. zero.
Chapter 27: Sources of the Magnetic
Field
Section 27-2: The Magnetic Field of
Currents: The Biot-Savart Law
Two wires lying in the plane of this page carry
equal currents in opposite directions, as shown. At
a point midway between the wires, the magnetic
field is
A. zero.
B. into the page.
C. out of the page.
D. toward the top or bottom of the page.
E. toward one of the two wires.
Two wires lying in the plane of this page carry
equal currents in opposite directions, as shown. At
a point midway between the wires, the magnetic
field is
A. zero.
B. into the page.
C. out of the page.
D. toward the top or bottom of the page.
E. toward one of the two wires.
What is the direction of the magnetic field around a
wire carrying a current perpendicularly into this
page?
A. The field is parallel to and in the same
direction as the current flow.
B. It is parallel to but directed opposite to the
current flow.
C. It is counterclockwise around the wire in the
plane of the page.
D. It is clockwise around the wire in the plane of
the page.
E. None of these is correct.
What is the direction of the magnetic field around a
wire carrying a current perpendicularly into this
page?
A. The field is parallel to and in the same
direction as the current flow.
B. It is parallel to but directed opposite to the
current flow.
C. It is counterclockwise around the wire in the
plane of the page.
D. It is clockwise around the wire in the
plane of the page.
E. None of these is correct.
A wire carries an electric current straight
upward. What is the direction of the
magnetic field due to the current north of the
wire?
A. north
B. east
C. west
D. south
E. upward
A wire carries an electric current straight
upward. What is the direction of the
magnetic field due to the current north of the
wire?
A. north
B. east
C. west
D. south
E. upward
The Biot–Savart law is similar to Coulomb's
law in that both
A. are inverse square laws.
B. include the permeability of free
space.
C. deal with excess charges.
D. are not electrical in nature.
E. are described by all of these.
The Biot–Savart law is similar to Coulomb's
law in that both
A. are inverse square laws.
B. include the permeability of free
space.
C. deal with excess charges.
D. are not electrical in nature.
E. are described by all of these.
Two current-carrying wires are perpendicular to
each other. The current in one flows vertically
upward and the current in the other flows
horizontally toward the east. The horizontal wire is
1 m south of the vertical wire. What is the direction
of the net magnetic force on the horizontal wire?
A. north
B. east
C. west
D. south
E. There is no net magnetic force on the
horizontal wire.
Two current-carrying wires are perpendicular to
each other. The current in one flows vertically
upward and the current in the other flows
horizontally toward the east. The horizontal wire is
1 m south of the vertical wire. What is the direction
of the net magnetic force on the horizontal wire?
A. north
B. east
C. west
D. south
E. There is no net magnetic force on the
horizontal wire.
Each of the figures shown is the source of a
magnetic field. In which figure does the magnetic
dipole vector point in the direction of the negative x
axis? (Note: in C and D the arrows show the
direction of the current.)
Each of the figures shown is the source of a
magnetic field. In which figure does the magnetic
dipole vector point in the direction of the negative x
axis? (Note: in C and D the arrows show the
direction of the current.)
The sketch shows a circular coil in the xz plane
carrying a current I. The direction of the
magnetic field at point O is
A. +x
B. –x
C. +y
D. –y
E. –z
The sketch shows a circular coil in the xz plane
carrying a current I. The direction of the
magnetic field at point O is
A. +x
B. –x
C. +y
D. –y
E. –z
In a circular loop of wire lying on a horizontal
floor, the current is constant and, to a person
looking downward, has a clockwise direction.
The accompanying magnetic field at the
center of the circle is directed
A. horizontally and to the east.
B. horizontally and to the north.
C. vertically upward.
D. parallel to the floor.
E. vertically downward.
In a circular loop of wire lying on a horizontal
floor, the current is constant and, to a person
looking downward, has a clockwise direction.
The accompanying magnetic field at the
center of the circle is directed
A. horizontally and to the east.
B. horizontally and to the north.
C. vertically upward.
D. parallel to the floor.
E. vertically downward.
An electron beam travels counterclockwise in a circle
of radius R in the magnetic field produced by the
Helmholtz coils as shown. If you increase the current
in the Helmholtz coils, the electron beam will
A. increase its radius.
B. decrease its radius.
C. maintain the same radius.
An electron beam travels counterclockwise in a circle
of radius R in the magnetic field produced by the
Helmholtz coils as shown. If you increase the current
in the Helmholtz coils, the electron beam will
A. increase its radius.
B. decrease its radius.
C. maintain the same radius.
Which graph best represents the strength of the
magnetic field B between the coils of radius R of a
Helmholtz pair as a function of distance along the
axis of the pair?
Which graph best represents the strength of the
magnetic field B between the coils of radius R of a
Helmholtz pair as a function of distance along the
axis of the pair?
An electron beam travels counterclockwise in a circle in the
magnetic field produced by the Helmholtz coils, as shown.
Assuming that the earth's field is downward, one can conclude that
A. the Helmholtz field equals
the earth's field.
B. the current in the coils
moves in the same
direction as the electron
beam.
C. the current in the coils
moves in the direction
opposite to the electron
beam.
D. the Helmholtz field curves
in the direction of the
electron beam.
E. the Helmholtz field curves
in a direction opposite to
the electron beam.
An electron beam travels counterclockwise in a circle in the
magnetic field produced by the Helmholtz coils, as shown.
Assuming that the earth's field is downward, one can conclude that
A. the Helmholtz field equals
the earth's field.
B. the current in the coils
moves in the same
direction as the electron
beam.
C. the current in the coils
moves in the direction
opposite to the electron
beam.
D. the Helmholtz field curves
in the direction of the
electron beam.
E. the Helmholtz field curves
in a direction opposite to
the electron beam.
When the positive current in a long wire is
flowing in a direction from S to N, it creates
a magnetic field below the wire that is
directed
A. from E to W.
B. from N to S.
C. from NE to SW.
D. from S to N.
E. from W to E.
When the positive current in a long wire is
flowing in a direction from S to N, it creates
a magnetic field below the wire that is
directed
A. from E to W.
B. from N to S.
C. from NE to SW.
D. from S to N.
E. from W to E.
The current in a wire along the x axis flows in the positive x
direction. If a proton, located as shown in the figure, has an
initial velocity in the positive z direction, it experiences
A.
B.
C.
D.
E.
a force in the direction of positive x.
a force in the direction of negative x.
a force in the direction of positive z.
a force in the direction of positive y.
no force.
The current in a wire along the x axis flows in the positive x
direction. If a proton, located as shown in the figure, has an
initial velocity in the positive z direction, it experiences
A.
B.
C.
D.
E.
a force in the direction of positive x.
a force in the direction of negative x.
a force in the direction of positive z.
a force in the direction of positive y.
no force.
A long conductor carrying current I lies in the xz
plane parallel to the z axis. The current travels in
the negative z direction, as shown in the figure.
The vector that represents the magnetic field at
the origin O is
A.
B.
C.
D.
E.

1

2

3

4

5
A long conductor carrying current I lies in the xz
plane parallel to the z axis. The current travels in
the negative z direction, as shown in the figure.
The vector that represents the magnetic field at
the origin O is
A.
B.
C.
D.
E.

1

2

3

4

5
Two straight wires perpendicular to the plane of this
page are shown in the figure. The currents in the wires
are the same. The current in M is into the page and the
current in N is out of the page. The vector that
represents the resultant magnetic field at point P is
D.

1

2

3

4
E.
None of these is correct.
A.
B.
C.
Two straight wires perpendicular to the plane of this
page are shown in the figure. The currents in the wires
are the same. The current in M is into the page and the
current in N is out of the page. The vector that
represents the resultant magnetic field at point P is
D.

1

2

3

4
E.
None of these is correct.
A.
B.
C.
Current-carrying wires are located along two
edges of a cube with the directions of the
currents as indicated. Which vector indicates
the resultant magnetic field at the corner of
the cube?
Current-carrying wires are located along two
edges of a cube with the directions of the
currents as indicated. Which vector indicates
the resultant magnetic field at the corner of
the cube?
Which graph best represents the magnetic field on
the axis inside a solenoid as a function of position x
on the axis?
Which graph best represents the magnetic field on
the axis inside a solenoid as a function of position x
on the axis?
The magnetic field at point P, due to the
current in the very long wire, varies with
distance R according to
A. R 2
B. R –3
C. R –2
D. R 3
E. R –1
The magnetic field at point P, due to the
current in the very long wire, varies with
distance R according to
A. R 2
B. R –3
C. R –2
D. R 3
E. R –1
Two parallel wires carry currents I1 and
I2 = 2I1 in the same direction. Which of
the following expressions shows the
relationship of the forces on the wires?
A. F1 = F2
B. F1 = 2F2
C. 2F1 = F2
D. F1 = 4F2
E. 4F1 = F2
Two parallel wires carry currents I1 and
I2 = 2I1 in the same direction. Which of
the following expressions shows the
relationship of the forces on the wires?
A. F1 = F2
B. F1 = 2F2
C. 2F1 = F2
D. F1 = 4F2
E. 4F1 = F2
Two very long, parallel conducting
wires carry equal currents in the
same direction, as shown. The
numbered diagrams show end
views of the wires and the
resultant force vectors due to
current flow in each wire. Which
diagram best represents the
direction of the forces?
Two very long, parallel conducting
wires carry equal currents in the
same direction, as shown. The
numbered diagrams show end
views of the wires and the
resultant force vectors due to
current flow in each wire. Which
diagram best represents the
direction of the forces?
Two very long, parallel conducting
wires carry equal currents in
opposite directions. The numbered
diagrams show end views of the
wires and the resultant force
vectors due to current flow in each
wire. Which diagram best
represents the direction of the
forces?
Two very long, parallel conducting
wires carry equal currents in
opposite directions. The numbered
diagrams show end views of the
wires and the resultant force
vectors due to current flow in each
wire. Which diagram best
represents the direction of the
forces?
Two horizontal straight rods 60 cm long are
separated by a vertical distance of 2.0 and
currents of 18 A each in opposite directions.
What mass must be placed on the upper rod
to balance the magnetic force of repulsion?
A. 0.50 g
B. 0.99 g
C. 9.7 g
D. 4.3 g
E. 1.6 g
Two horizontal straight rods 60 cm long are
separated by a vertical distance of 2.0 and
currents of 18 A each in opposite directions.
What mass must be placed on the upper rod
to balance the magnetic force of repulsion?
A. 0.50 g
B. 0.99 g
C. 9.7 g
D. 4.3 g
E. 1.6 g
Calculate the magnetic field at the center of a
circular current loop of radius R divided by the
magnetic field at a distance R away from a very
long straight wire carrying the same current
value I. (Note the loop and wire are not in
electrical contact.)
A.
B.
C.
D.
E.
3.14
1.00
2.00
0.318
0.500
Calculate the magnetic field at the center of a
circular current loop of radius R divided by the
magnetic field at a distance R away from a very
long straight wire carrying the same current
value I. (Note the loop and wire are not in
electrical contact.)
A.
B.
C.
D.
E.
3.14
1.00
2.00
0.318
0.500
Chapter 27: Sources of the Magnetic
Field
Section 27-4: Ampere’s Law
Ampere's law is valid
A. when there is a high degree of
symmetry in the geometry of the
situation.
B. when there is no symmetry.
C. when the current is constant.
D. when the magnetic field is constant.
E. for all of these conditions.
Ampere's law is valid
A. when there is a high degree of
symmetry in the geometry of the
situation.
B. when there is no symmetry.
C. when the current is constant.
D. when the magnetic field is constant.
E. for all of these conditions.
Which graph best
represents B as a
function of r for a
wire of radius R
carrying a current
I uniformly
distributed over
its cross-sectional
area?
Which graph best
represents B as a
function of r for a
wire of radius R
carrying a current
I uniformly
distributed over
its cross-sectional
area?
Chapter 27: Sources of the Magnetic
Field
Section 27-5: Magnetism in Matter
The orbital magnetic moment of an atomic
electron is
A. directly proportional to its angular
momentum.
B. directly proportional to the electronic charge.
C. inversely proportional to the mass of the
electron.
D. quantized as a consequence of the
quantization of angular momentum.
E. described by all of the above.
The orbital magnetic moment of an atomic
electron is
A. directly proportional to its angular
momentum.
B. directly proportional to the electronic charge.
C. inversely proportional to the mass of the
electron.
D. quantized as a consequence of the
quantization of angular momentum.
E. described by all of the above.
Diamagnetic materials
A. have small negative values of magnetic
susceptibility.
B. are those in which the magnetic moments of all
electrons in each atom cancel.
C. experience a small induced magnetic moment
when placed in an external magnetic field.
D. exhibit the property of diamagnetism
independently of temperature.
E. are described by all of the above.
Diamagnetic materials
A. have small negative values of magnetic
susceptibility.
B. are those in which the magnetic moments of all
electrons in each atom cancel.
C. experience a small induced magnetic moment
when placed in an external magnetic field.
D. exhibit the property of diamagnetism
independently of temperature.
E. are described by all of the above.
If the magnetic susceptibility of a material is
positive,
A. paramagnetic effects must be greater than
diamagnetic effects.
B. diamagnetic effects must be greater than
paramagnetic effects.
C. diamagnetic effects must be greater than
ferromagnetic effects.
D. ferromagnetic effects must be greater than
paramagnetic effects.
E. paramagnetic effects must be greater than
ferromagnetic effects.
If the magnetic susceptibility of a material is
positive,
A. paramagnetic effects must be greater
than diamagnetic effects.
B. diamagnetic effects must be greater than
paramagnetic effects.
C. diamagnetic effects must be greater than
ferromagnetic effects.
D. ferromagnetic effects must be greater than
paramagnetic effects.
E. paramagnetic effects must be greater than
ferromagnetic effects.
Which of the following statements is false?
A. When an electric field is applied to a dielectric,
the resultant electric field is always less than the
applied.
B. When a magnetic field is applied to a
paramagnetic material, the resultant magnetic
field is always more than the applied.
C. When a magnetic field is applied to a
diamagnetic material, the resultant magnetic
field is always less than the applied.
D. When a magnetic field is applied to a
ferromagnetic material, the resultant magnetic
field is always more than the applied.
Which of the following statements is false?
A. When an electric field is applied to a dielectric,
the resultant electric field is always less than the
applied.
B. When a magnetic field is applied to a
paramagnetic material, the resultant magnetic
field is always more than the applied.
C. When a magnetic field is applied to a
diamagnetic material, the resultant magnetic
field is always less than the applied.
D. When a magnetic field is applied to a
ferromagnetic material, the resultant
magnetic field is always more than the
applied.
You place a substance in an external magnetic field
and find that it is attracted to the field but only to a
limited degree because of thermal agitation effects
which do not permit atomic dipoles to align
completely with the field. This substance is
A. diamagnetic
B. paramagnetic
C. permamagnetic
D. ferromagnetic
E. antimagnetic
You place a substance in an external magnetic field
and find that it is attracted to the field but only to a
limited degree because of thermal agitation effects
which do not permit atomic dipoles to align
completely with the field. This substance is
A. diamagnetic
B. paramagnetic
C. permamagnetic
D. ferromagnetic
E. antimagnetic
Point P1 on the hysteresis curve corresponds to
A. approximate saturation.
B. the alignment of nearly all atomic
magnetic moments.
C. maximum applied magnetic field.
D. the alignment of virtually all the
magnetic domains.
E. All of these are correct.
Point P1 on the hysteresis curve corresponds to
A. approximate saturation.
B. the alignment of nearly all atomic
magnetic moments.
C. maximum applied magnetic field.
D. the alignment of virtually all the
magnetic domains.
E. All of these are correct.
If you assume that the scalings of the axes of these
hysteresis curves are the same, you can conclude that
A. curve 1 is for a magnetically softer material than for
curve 2.
B. curve 2 is for a magnetically softer material than for
curve 1.
C. both curves are for equally magnetically soft
materials.
If you assume that the scalings of the axes of these
hysteresis curves are the same, you can conclude that
A. curve 1 is for a magnetically softer material than for
curve 2.
B. curve 2 is for a magnetically softer material than
for curve 1.
C. both curves are for equally magnetically soft
materials.
Some substances, when placed in a
magnetic field in free space, reduce the
magnitude of the magnetic induction in the
space they occupy. These substances are
A. ferromagnetic
B. not magnetic
C. ultramagnetic
D. paramagnetic
E. diamagnetic
Some substances, when placed in a
magnetic field in free space, reduce the
magnitude of the magnetic induction in the
space they occupy. These substances are
A. ferromagnetic
B. not magnetic
C. ultramagnetic
D. paramagnetic
E. diamagnetic
Diamagnetic materials
A. have positive values of magnetic
susceptibility χm.
B. have negative values of magnetic
susceptibility χm.
C. have a magnetic susceptibility of χm = 0.
Diamagnetic materials
A. have positive values of magnetic
susceptibility χm.
B. have negative values of magnetic
susceptibility χm.
C. have a magnetic susceptibility of χm = 0.